Fix partial painting with render pipeline throttling

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

 // Copyright 2015 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 "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/frame/FrameView.h"
 #include "core/html/HTMLIFrameElement.h"
 #include "platform/testing/URLTestHelpers.h"
 #include "platform/testing/UnitTestHelpers.h"
@@ skipping 193 matching lines @@
 
     // Move the frame offscreen to throttle it.
     frameElement->setAttribute(styleAttr, "transform: translateY(480px)");
     compositeFrame();
     EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
 
     // Mutating the throttled frame should not cause an animation to be scheduled.
     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());
 
     // The first frame we composite after unthrottling won't contain the
     // frame's new contents because unthrottling happens at the end of the
     // lifecycle update. We need to do another composite to refresh the frame's
     // contents.
     auto displayItems2 = compositeFrame();
     EXPECT_FALSE(displayItems2.contains(SimCanvas::Rect, "green"));
     EXPECT_TRUE(compositor().needsAnimate());
@@ skipping 19 matching lines @@
 
     // Change the size of a div in the throttled frame.
     auto* divElement = frameElement->contentDocument()->getElementById("div");
     divElement->setAttribute(styleAttr, "width: 50px");
 
     // Querying the width of the div should do a synchronous layout update even
     // though the frame is being throttled.
     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;
     WebViewImpl* webView = WebViewImpl::create(&viewClient);
     webView->resize(WebSize(640, 480));
 
     // Create a remote root frame with a local child frame.
     FrameTestHelpers::TestWebRemoteFrameClient remoteClient;
     webView->setMainFrame(remoteClient.frame());
     remoteClient.frame()->setReplicatedOrigin(WebSecurityOrigin::createUnique());
@@ skipping 27 matching lines @@
 
     // Update the lifecycle again. The frame's lifecycle should not advance
     // because of throttling even though it is the local root.
     frameView->updateAllLifecyclePhases();
     testing::runPendingTasks();
     EXPECT_EQ(DocumentLifecycle::VisualUpdatePending, frameDocument->lifecycle().state());
     webView->close();
 }
 
 } // namespace blink