[blink] Request compositing update when canvas hibernates/wakes up.

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 56a560a7c820e8756635b2364df77ee5dba9bc33..4bb1435a00013b0000c33fa232228fd1a40d971b 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -1216,6 +1216,8 @@ void HTMLCanvasElement::pageVisibilityChanged() {
       discardImageBuffer();
     }
   }
+  // If visibility changes, shouldBeDirectComposited() may change.
+  setNeedsCompositingUpdate();

[chrishtr, 2017/04/07 17:12:32]

Which of the conditions below depend on page visibility?

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/html/HTML...

[Eric Seckler, 2017/04/07 17:27:11]

CanvasRenderingContext2D::isComposited() -> isAccelerated() ->
ImageBuffer::isAccelerated() -> Canvas2DImageBufferSurface::isAccelerated() ->
Canvas2DLayerBridge::isAccelerated() -> isHibernating()

And Canvas2DLayerBridge::hibernate() is eventually called by setIsHidden()
above.

 }
 
 void HTMLCanvasElement::contextDestroyed(ExecutionContext*) {