Don't allow the composited-alpha folding optimization to cross subsequences

third_party/WebKit/Source/platform/graphics/paint/PaintControllerTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/graphics/paint/PaintController.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/paint/ClipPathDisplayItem.h"
 #include "platform/graphics/paint/ClipPathRecorder.h"
@@ skipping 2095 matching lines @@
              FloatRect(100, 100, 300, 300));
     DrawRect(context, first, kForegroundDrawingType,
              FloatRect(100, 100, 300, 300));
     GetPaintController().CommitNewDisplayItems();
     DrawRect(context, first, kBackgroundDrawingType,
              FloatRect(100, 100, 300, 300));
     GetPaintController().CommitNewDisplayItems();
   }
 
   void TestNoopPairsInSubsequence() {
+    EXPECT_FALSE(GetPaintController().LastDisplayItemIsSubsequenceEnd());
+
     FakeDisplayItemClient container("container");
     GraphicsContext context(GetPaintController());
 
     {
       SubsequenceRecorder r(context, container);
       DrawRect(context, container, kBackgroundDrawingType,
                FloatRect(100, 100, 100, 100));
     }
     GetPaintController().CommitNewDisplayItems();
 
     EXPECT_FALSE(SubsequenceRecorder::UseCachedSubsequenceIfPossible(
         context, container));
     {
       // Generate some no-op pairs which should not affect under-invalidation
       // checking.
       ClipRecorder r1(context, container, kClipType, IntRect(1, 1, 9, 9));
       ClipRecorder r2(context, container, kClipType, IntRect(1, 1, 2, 2));
       ClipRecorder r3(context, container, kClipType, IntRect(1, 1, 3, 3));
       ClipPathRecorder r4(context, container, Path());
     }
     {
       EXPECT_FALSE(SubsequenceRecorder::UseCachedSubsequenceIfPossible(
           context, container));
       SubsequenceRecorder r(context, container);
       DrawRect(context, container, kBackgroundDrawingType,
                FloatRect(100, 100, 100, 100));
     }
+    EXPECT_TRUE(GetPaintController().LastDisplayItemIsSubsequenceEnd());
+
     GetPaintController().CommitNewDisplayItems();
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
     DisplayItemClient::EndShouldKeepAliveAllClients();
 #endif
   }
 
   void TestChangeDrawingInSubsequence() {
     FakeDisplayItemClient first("first");
     GraphicsContext context(GetPaintController());
@@ skipping 207 matching lines @@
 }
 
 TEST_F(PaintControllerUnderInvalidationTest,
        FoldCompositingDrawingInSubsequence) {
   TestFoldCompositingDrawingInSubsequence();
 }
 
 #endif  // defined(GTEST_HAS_DEATH_TEST) && !OS(ANDROID)
 
 }  // namespace blink