[inspector] entered into context before getPossibleBreakpoints call

getPossibleBreakpoints implementation can enforce function compilation which potentially can produce syntax error, we need to have a context to correctly report this error.

BUG=chromium:715334
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2851853002
Cr-Commit-Position: refs/heads/master@{#45003}

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

@@ -456,11 +456,15 @@ Response V8DebuggerAgentImpl::getPossibleBreakpoints(
   }
   auto it = m_scripts.find(scriptId);
   if (it == m_scripts.end()) return Response::Error("Script not found");
-
   std::vector<v8::debug::BreakLocation> v8Locations;
-  if (!it->second->getPossibleBreakpoints(
-          v8Start, v8End, restrictToFunction.fromMaybe(false), &v8Locations)) {
-    return Response::InternalError();
+  {
+    v8::HandleScope handleScope(m_isolate);
+    v8::Local<v8::Context> debuggerContext =
+        v8::debug::GetDebugContext(m_isolate);
+    v8::Context::Scope contextScope(debuggerContext);
+    v8::TryCatch tryCatch(m_isolate);
+    it->second->getPossibleBreakpoints(
+        v8Start, v8End, restrictToFunction.fromMaybe(false), &v8Locations);
   }
 
   *locations = protocol::Array<protocol::Debugger::BreakLocation>::create();

test/inspector/debugger/get-possible-breakpoints-lazy-error-expected.txt

+getPossibleBreakpoints should not crash during lazy compilation (crbug.com/715334)
+{
+    method : Debugger.scriptParsed
+    params : {
+        endColumn : 21
+        endLine : 2
+        executionContextId : <executionContextId>
+        hasSourceURL : true
+        hash : FA2A959297747012766FE9C5006E7F522D88FA72
+        isLiveEdit : false
+        isModule : false
+        length : 52
+        scriptId : <scriptId>
+        sourceMapURL : 
+        startColumn : 0
+        startLine : 0
+        url : test.js
+    }
+}
+{
+    id : <messageId>
+    result : {
+        locations : [
+        ]
+    }
+}

test/inspector/debugger/get-possible-breakpoints-lazy-error.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+InspectorTest.log('getPossibleBreakpoints should not crash during lazy compilation (crbug.com/715334)');
+
+InspectorTest.addScript(`
+function test() { continue; }
+//# sourceURL=test.js`);
+
+(async function test() {
+  Protocol.Debugger.enable();
+  let script = await Protocol.Debugger.onceScriptParsed();
+  InspectorTest.logMessage(script);
+  let scriptId = script.params.scriptId;
+  Protocol.Debugger.onScriptFailedToParse(msg => {
+    InspectorTest.logMessage(msg);
+    if (msg.params.scriptId !== script.params.scriptId) {
+      InspectorTest.log('Failed script to parse event has different scriptId');
+    } else {
+      InspectorTest.log('One script is reported twice');
+    }
+  });
+  let response = await Protocol.Debugger.getPossibleBreakpoints({
+    start: {scriptId, lineNumber: 0, columnNumber: 0}});
+  InspectorTest.logMessage(response);
+  InspectorTest.completeTest();
+})();