Use intersection observer to control frame throttling

third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp

Index: third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp b/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
index b2e6e095f0f9840e161dccf0f2c46bc41dcfda51..5752b1b118c715fec5eab2283d0edcbdf89aec53 100644
--- a/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
+++ b/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
@@ -778,7 +778,7 @@ TEST_F(FrameThrottlingTest, ThrottleSubtreeAtomically) {
   // observer notifications.
   frameElement->contentDocument()
       ->view()
-      ->notifyRenderThrottlingObserversForTesting();
+      ->updateRenderThrottlingStatusForTesting();
   EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
   EXPECT_TRUE(
       childFrameElement->contentDocument()->view()->canThrottleRendering());
@@ -786,10 +786,34 @@ TEST_F(FrameThrottlingTest, ThrottleSubtreeAtomically) {
   // Both frames should still be throttled after the second notification.
   childFrameElement->contentDocument()
       ->view()
-      ->notifyRenderThrottlingObserversForTesting();
+      ->updateRenderThrottlingStatusForTesting();
   EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
   EXPECT_TRUE(
       childFrameElement->contentDocument()->view()->canThrottleRendering());
+
+  // Move the frame back on screen but don't update throttling yet.
+  frameElement->setAttribute(styleAttr, "transform: translateY(0px)");
+  compositor().beginFrame();
+  EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
+  EXPECT_TRUE(
+      childFrameElement->contentDocument()->view()->canThrottleRendering());
+
+  // Update throttling for the child. It should remain throttled because the
+  // parent is still throttled.
+  childFrameElement->contentDocument()
+      ->view()
+      ->updateRenderThrottlingStatusForTesting();
+  EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
+  EXPECT_TRUE(
+      childFrameElement->contentDocument()->view()->canThrottleRendering());
+
+  // Updating throttling on the parent should unthrottle both frames.
+  frameElement->contentDocument()
+      ->view()
+      ->updateRenderThrottlingStatusForTesting();
+  EXPECT_FALSE(frameElement->contentDocument()->view()->canThrottleRendering());
+  EXPECT_FALSE(
+      childFrameElement->contentDocument()->view()->canThrottleRendering());
 }
 
 TEST_F(FrameThrottlingTest, SkipPaintingLayersInThrottledFrames) {