Revert "Reland#2 [parser] Refactor streaming scanner streams."

This reverts commit de9269f3.

Something's still wrong in the encoding handling (see bug).

Bug: chromium:763106
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Icd19dd42b84b9d090e191375a2942b9941110bcf
Reviewed-on: https://chromium-review.googlesource.com/657386
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47924}

include/v8.h

@@ -1358,6 +1358,11 @@ class V8_EXPORT ScriptCompiler {
      * length of the data returned. When the data ends, GetMoreData should
      * return 0. Caller takes ownership of the data.
      *
+     * When streaming UTF-8 data, V8 handles multi-byte characters split between
+     * two data chunks, but doesn't handle multi-byte characters split between
+     * more than two data chunks. The embedder can avoid this problem by always
+     * returning at least 2 bytes of data.
+     *
      * If the embedder wants to cancel the streaming, they should make the next
      * GetMoreData call return 0. V8 will interpret it as end of data (and most
      * probably, parsing will fail). The streaming task will return as soon as

test/cctest/parsing/test-scanner-streams.cc

@@ -39,13 +39,6 @@ class ChunkSource : public v8::ScriptCompiler::ExternalSourceStream {
     }
     chunks_.push_back({nullptr, 0});
   }
-  ChunkSource(const uint8_t* data, size_t len, size_t chunk_size)
-      : current_(0) {
-    for (size_t i = 0; i < len; i += chunk_size) {
-      chunks_.push_back({data + i, i::Min(chunk_size, len - i)});
-    }
-    chunks_.push_back({nullptr, 0});
-  }
   ~ChunkSource() {}
   bool SetBookmark() override { return false; }
   void ResetToBookmark() override {}
@@ -445,18 +438,6 @@ TEST(CharacterStreams) {
   TestCharacterStreams(buffer, arraysize(buffer) - 1, 576, 3298);
 }
 
-TEST(Uft8MultipleBOMChunks) {
-  const char* chunks = "\xef\xbb\xbf\0\xef\xbb\xbf\0\xef\xbb\xbf\0a\0";
-  const uint16_t unicode[] = {0xFEFF, 0xFEFF, 97};
-  ChunkSource chunk_source(chunks);
-  std::unique_ptr<i::Utf16CharacterStream> stream(i::ScannerStream::For(
-      &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
-  for (size_t i = 0; i < arraysize(unicode); i++) {
-    CHECK_EQ(unicode[i], stream->Advance());
-  }
-  CHECK_EQ(i::Utf16CharacterStream::kEndOfInput, stream->Advance());
-}
-
 // Regression test for crbug.com/651333. Read invalid utf-8.
 TEST(Regress651333) {
   const uint8_t bytes[] =
@@ -498,17 +479,10 @@ TEST(Regress6377) {
       "\x80"            // second chunk - one-byte end of 4-byte seq
       "a\xc3\0"         // and an 'a' + start of 2-byte seq
       "\xbf\0",         // third chunk - end of 2-byte seq
-
-      // Regression test for
-      // https://bugs.chromium.org/p/chromium/issues/detail?id=758508
-      "X\xef\xbb\xbfX\0",  // first chunk - no BOM but U+feff in the middle
   };
   const std::vector<std::vector<uint16_t>> unicode = {
-      {0xd800, 0xdc00, 97},
-      {0xfff, 97},
-      {0xff, 97},
-      {0xd800, 0xdc00, 97, 0xff},
-      {88, 0xfeff, 88}};
+      {0xd800, 0xdc00, 97}, {0xfff, 97}, {0xff, 97}, {0xd800, 0xdc00, 97, 0xff},
+  };
   CHECK_EQ(unicode.size(), sizeof(cases) / sizeof(cases[0]));
   for (size_t c = 0; c < unicode.size(); ++c) {
     ChunkSource chunk_source(cases[c]);
@@ -525,36 +499,3 @@ TEST(Regress6377) {
     CHECK_EQ(i::Utf16CharacterStream::kEndOfInput, stream->Advance());
   }
 }
-
-TEST(Regress724166) {
-  // Chunk size has to be multiple of kBufferCharacterSize
-  constexpr size_t kBufferCharacterSize = 512;
-  constexpr size_t kChunkSize = kBufferCharacterSize * 8;
-  constexpr size_t kChunks = 4;
-  uint8_t buffer[kChunkSize * kChunks];
-  for (size_t j = 0; j < kChunks; ++j) {
-    for (size_t i = 0; i < kChunkSize; ++i) {
-      buffer[kChunkSize * j + i] = (i % 0x7e) + 1;
-    }
-  }
-  // Add BOM at the beginning
-  buffer[0] = '\xef';
-  buffer[1] = '\xbb';
-  buffer[2] = '\xbf';
-  ChunkSource chunk_source(buffer, arraysize(buffer), kChunkSize);
-  std::unique_ptr<i::Utf16CharacterStream> stream(i::ScannerStream::For(
-      &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
-  for (size_t i = 0; i < arraysize(buffer) - 3; ++i) {
-    CHECK_EQ(static_cast<i::uc32>(buffer[i + 3]), stream->Advance());
-  }
-  CHECK_EQ(i::Utf16CharacterStream::kEndOfInput, stream->Advance());
-  for (int z = -8; z < 8; ++z) {
-    for (size_t j = kBufferCharacterSize + z; j < arraysize(buffer);
-         j += kBufferCharacterSize) {
-      stream->Seek(j);
-      for (size_t i = j; i < arraysize(buffer) - 3; ++i) {
-        CHECK_EQ(static_cast<i::uc32>(buffer[i + 3]), stream->Advance());
-      }
-    }
-  }
-}