Reland "inspector: do not convert and store String16 for script source"

This is a reland of e987606a

Original change's description:
> inspector: do not convert and store String16 for script source
>
> We need script source for:
> - calculating hash to report as part of scriptParsed event,
> - reporting it as response on getScriptSource request,
> - searching inside as response on searchInContent request,
> - breakpoints hints.
>
> In all cases there is no need to store source on inspector side.
>
> R=alph@chromium.org
>
> Bug: chromium:873865,v8:7731
> Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
> Change-Id: Ice24ddc72cfff36fb9a2dff2d7c4543defe3f668
> Reviewed-on: https://chromium-review.googlesource.com/1182603
> Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
> Reviewed-by: Alexei Filippov <alph@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55286}

TBR=alph@chromium.org

Bug: chromium:873865, v8:7731
Change-Id: I0a0e93cd9d7797e4b3c57b1ab4f1a20af27fea9c
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1195907Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55509}

src/inspector/v8-debugger-agent-impl.cc

@@ -160,9 +160,8 @@ String16 breakpointHint(const V8DebuggerScript& script, int lineNumber,
                         int columnNumber) {
   int offset = script.offset(lineNumber, columnNumber);
   if (offset == V8DebuggerScript::kNoOffset) return String16();
-  const String16& source = script.source();
   String16 hint =
-      source.substring(offset, kBreakpointHintMaxLength).stripWhiteSpace();
+      script.source(offset, kBreakpointHintMaxLength).stripWhiteSpace();
   for (size_t i = 0; i < hint.length(); ++i) {
     if (hint[i] == '\r' || hint[i] == '\n' || hint[i] == ';') {
       return hint.substring(0, i);
@@ -183,8 +182,8 @@ void adjustBreakpointLocation(const V8DebuggerScript& script,
   intptr_t searchRegionOffset = std::max(
       sourceOffset - kBreakpointHintMaxSearchOffset, static_cast<intptr_t>(0));
   size_t offset = sourceOffset - searchRegionOffset;
-  String16 searchArea = script.source().substring(
-      searchRegionOffset, offset + kBreakpointHintMaxSearchOffset);
+  String16 searchArea = script.source(searchRegionOffset,
+                                      offset + kBreakpointHintMaxSearchOffset);
 
   size_t nextMatch = searchArea.find(hint, offset);
   size_t prevMatch = searchArea.reverseFind(hint, offset);
@@ -837,7 +836,7 @@ Response V8DebuggerAgentImpl::searchInContent(
     return Response::Error("No script for id: " + scriptId);
 
   std::vector<std::unique_ptr<protocol::Debugger::SearchMatch>> matches =
-      searchInTextByLinesImpl(m_session, it->second->source(), query,
+      searchInTextByLinesImpl(m_session, it->second->source(0), query,
                               optionalCaseSensitive.fromMaybe(false),
                               optionalIsRegex.fromMaybe(false));
   *results = protocol::Array<protocol::Debugger::SearchMatch>::create();
@@ -927,7 +926,7 @@ Response V8DebuggerAgentImpl::getScriptSource(const String16& scriptId,
   ScriptsMap::iterator it = m_scripts.find(scriptId);
   if (it == m_scripts.end())
     return Response::Error("No script for id: " + scriptId);
-  *scriptSource = it->second->source();
+  *scriptSource = it->second->source(0);
   return Response::OK();
 }
 
@@ -1434,8 +1433,7 @@ void V8DebuggerAgentImpl::didParseSource(
           scriptRef->endLine(), scriptRef->endColumn(), contextId,
           scriptRef->hash(), std::move(executionContextAuxDataParam),
           isLiveEditParam, std::move(sourceMapURLParam), hasSourceURLParam,
-          isModuleParam, static_cast<int>(scriptRef->source().length()),
-          std::move(stackTrace));
+          isModuleParam, scriptRef->length(), std::move(stackTrace));
     }
   } else {
     m_frontend.scriptFailedToParse(
@@ -1443,7 +1441,7 @@ void V8DebuggerAgentImpl::didParseSource(
         scriptRef->endLine(), scriptRef->endColumn(), contextId,
         scriptRef->hash(), std::move(executionContextAuxDataParam),
         std::move(sourceMapURLParam), hasSourceURLParam, isModuleParam,
-        static_cast<int>(scriptRef->source().length()), std::move(stackTrace));
+        scriptRef->length(), std::move(stackTrace));
   }
 
   if (!success) {

src/inspector/v8-debugger-script.cc

@@ -20,7 +20,7 @@ const char kGlobalDebuggerScriptHandleLabel[] = "DevTools debugger";
 // Multiplikation in
 // eingeschränkten Branchingprogrammmodellen" by Woelfe.
 // http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
-String16 calculateHash(const String16& str) {
+String16 calculateHash(v8::Isolate* isolate, v8::Local<v8::String> source) {
   static uint64_t prime[] = {0x3FB75161, 0xAB1F4E4F, 0x82675BC5, 0xCD924D35,
                              0x81ABE279};
   static uint64_t random[] = {0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476,
@@ -34,9 +34,14 @@ String16 calculateHash(const String16& str) {
   const size_t hashesSize = arraysize(hashes);
 
   size_t current = 0;
+
+  std::unique_ptr<UChar[]> buffer(new UChar[source->Length()]);
+  int written = source->Write(
+      isolate, reinterpret_cast<uint16_t*>(buffer.get()), 0, source->Length());
+
   const uint32_t* data = nullptr;
-  size_t sizeInBytes = sizeof(UChar) * str.length();
-  data = reinterpret_cast<const uint32_t*>(str.characters16());
+  size_t sizeInBytes = sizeof(UChar) * written;
+  data = reinterpret_cast<const uint32_t*>(buffer.get());
   for (size_t i = 0; i < sizeInBytes / 4; ++i) {
     uint32_t d = v8::internal::ReadUnalignedUInt32(
         reinterpret_cast<v8::internal::Address>(data + i));
@@ -121,12 +126,29 @@ class ActualScript : public V8DebuggerScript {
   bool isLiveEdit() const override { return m_isLiveEdit; }
   bool isModule() const override { return m_isModule; }
 
-  const String16& source() const override { return m_source; }
+  String16 source(size_t pos, size_t len) const override {
+    v8::HandleScope scope(m_isolate);
+    v8::Local<v8::String> v8Source;
+    if (!script()->Source().ToLocal(&v8Source)) return String16();
+    if (pos >= static_cast<size_t>(v8Source->Length())) return String16();
+    size_t substringLength =
+        std::min(len, static_cast<size_t>(v8Source->Length()) - pos);
+    std::unique_ptr<UChar[]> buffer(new UChar[substringLength]);
+    v8Source->Write(m_isolate, reinterpret_cast<uint16_t*>(buffer.get()),
+                    static_cast<int>(pos), static_cast<int>(substringLength));
+    return String16(buffer.get(), substringLength);
+  }
   int startLine() const override { return m_startLine; }
   int startColumn() const override { return m_startColumn; }
   int endLine() const override { return m_endLine; }
   int endColumn() const override { return m_endColumn; }
   bool isSourceLoadedLazily() const override { return false; }
+  int length() const override {
+    v8::HandleScope scope(m_isolate);
+    v8::Local<v8::String> v8Source;
+    if (!script()->Source().ToLocal(&v8Source)) return 0;
+    return v8Source->Length();
+  }
 
   const String16& sourceMappingURL() const override {
     return m_sourceMappingURL;
@@ -213,7 +235,13 @@ class ActualScript : public V8DebuggerScript {
   }
 
   const String16& hash() const override {
-    if (m_hash.isEmpty()) m_hash = calculateHash(source());
+    if (m_hash.isEmpty()) {
+      v8::HandleScope scope(m_isolate);
+      v8::Local<v8::String> v8Source;
+      if (script()->Source().ToLocal(&v8Source)) {
+        m_hash = calculateHash(m_isolate, v8Source);
+      }
+    }
     DCHECK(!m_hash.isEmpty());
     return m_hash;
   }
@@ -264,10 +292,6 @@ class ActualScript : public V8DebuggerScript {
 
     USE(script->ContextId().To(&m_executionContextId));
 
-    if (script->Source().ToLocal(&tmp)) {
-      m_source = toProtocolString(m_isolate, tmp);
-    }
-
     m_isModule = script->IsModule();
 
     m_script.Reset(m_isolate, script);
@@ -277,7 +301,6 @@ class ActualScript : public V8DebuggerScript {
   String16 m_sourceMappingURL;
   bool m_isLiveEdit = false;
   bool m_isModule = false;
-  String16 m_source;
   mutable String16 m_hash;
   int m_startLine = 0;
   int m_startColumn = 0;
@@ -309,8 +332,9 @@ class WasmVirtualScript : public V8DebuggerScript {
     UNREACHABLE();
   }
   bool isSourceLoadedLazily() const override { return true; }
-  const String16& source() const override {
-    return m_wasmTranslation->GetSource(m_id, m_functionIndex);
+  String16 source(size_t pos, size_t len) const override {
+    return m_wasmTranslation->GetSource(m_id, m_functionIndex)
+        .substring(pos, len);
   }
   int startLine() const override {
     return m_wasmTranslation->GetStartLine(m_id, m_functionIndex);
@@ -324,6 +348,9 @@ class WasmVirtualScript : public V8DebuggerScript {
   int endColumn() const override {
     return m_wasmTranslation->GetEndColumn(m_id, m_functionIndex);
   }
+  int length() const override {
+    return static_cast<int>(source(0, UINT_MAX).length());
+  }
 
   bool getPossibleBreakpoints(
       const v8::debug::Location& start, const v8::debug::Location& end,

src/inspector/v8-debugger-script.h

@@ -60,7 +60,7 @@ class V8DebuggerScript {
   const String16& sourceURL() const { return m_url; }
 
   virtual const String16& sourceMappingURL() const = 0;
-  virtual const String16& source() const = 0;
+  virtual String16 source(size_t pos, size_t len = UINT_MAX) const = 0;
   virtual const String16& hash() const = 0;
   virtual int startLine() const = 0;
   virtual int startColumn() const = 0;
@@ -70,6 +70,7 @@ class V8DebuggerScript {
   virtual bool isLiveEdit() const = 0;
   virtual bool isModule() const = 0;
   virtual bool isSourceLoadedLazily() const = 0;
+  virtual int length() const = 0;
 
   void setSourceURL(const String16&);
   virtual void setSourceMappingURL(const String16&) = 0;