Fix partial painting with render pipeline 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 beca4dd5faba0d8e57f0e39b2aa12e710fb4f5f1..7ead20d2c0e74b269da8a7c6c1abf43d46de7f90 100644
--- a/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
+++ b/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
@@ -211,7 +211,7 @@ TEST_F(FrameThrottlingTest, MutatingThrottledFrameDoesNotCauseAnimation)
     frameElement->contentDocument()->documentElement()->setAttribute(styleAttr, "background: green");
     EXPECT_FALSE(compositor().needsAnimate());
 
-    // Moving the frame back on screen to unthrottle it.
+    // Move the frame back on screen to unthrottle it.
     frameElement->setAttribute(styleAttr, "");
     EXPECT_TRUE(compositor().needsAnimate());
 
@@ -251,6 +251,34 @@ TEST_F(FrameThrottlingTest, SynchronousLayoutInThrottledFrame)
     EXPECT_EQ(50, divElement->clientWidth());
 }
 
+TEST_F(FrameThrottlingTest, UnthrottlingTriggersRepaint)
+{
+    // Create a hidden frame which is throttled.
+    SimRequest mainResource("https://example.com/", "text/html");
+    SimRequest frameResource("https://example.com/iframe.html", "text/html");
+
+    loadURL("https://example.com/");
+    mainResource.complete("<iframe id=frame sandbox src=iframe.html></iframe>");
+    frameResource.complete("<style> html { background: green; } </style>");
+
+    // Move the frame offscreen to throttle it.
+    auto* frameElement = toHTMLIFrameElement(document().getElementById("frame"));
+    frameElement->setAttribute(styleAttr, "transform: translateY(480px)");
+    EXPECT_FALSE(frameElement->contentDocument()->view()->shouldThrottleRendering());
+    compositeFrame();
+    EXPECT_TRUE(frameElement->contentDocument()->view()->shouldThrottleRendering());
+
+    // Scroll down to unthrottle the frame. The first frame we composite after
+    // scrolling won't contain the frame yet, but will schedule another repaint.
+    webView().mainFrameImpl()->frameView()->setScrollPosition(DoublePoint(0, 480), ProgrammaticScroll);
+    auto displayItems = compositeFrame();
+    EXPECT_FALSE(displayItems.contains(SimCanvas::Rect, "green"));
+
+    // Now the frame contents should be visible again.
+    auto displayItems2 = compositeFrame();
+    EXPECT_TRUE(displayItems2.contains(SimCanvas::Rect, "green"));
+}
+

[Xianzhu, 2016/01/25 18:33:17]

Can you add a test for the following scenario (or please ignore this if there is
already one):

- A frame is not throttled;
- the frame becomes throttled;
- some object changes style in the frame;
- the frame becomes not throttled;
ensure the object changed style is painted with the new style.

Based on the code this seems to work because we paint nothing (so cache nothing)
for throttled frames, but perhaps in the future we could cache the previous
non-throttled painted results.

[Sami, 2016/01/25 18:44:23]

Great idea, done.

 TEST(RemoteFrameThrottlingTest, ThrottledLocalRoot)
 {
     FrameTestHelpers::TestWebViewClient viewClient;