Disallow throttling while running requestAnimationFrame callbacks

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 ae063ee128ba1fe7491c4ff8669534796e37d68c..dc31adacdf21f618f6bc9328d26e08cf3e2f8e4f 100644
--- a/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
+++ b/third_party/WebKit/Source/web/tests/FrameThrottlingTest.cpp
@@ -809,4 +809,52 @@ TEST_F(FrameThrottlingTest, SkipPaintingLayersInThrottledFrames)
     EXPECT_FALSE(displayItems2.contains(SimCanvas::Rect, "red"));
 }
 
+TEST_F(FrameThrottlingTest, SynchronousLayoutInRequestAnimationFrameCallback)
+{
+    webView().settings()->setJavaScriptEnabled(true);
+
+    // Prepare a page with two cross origin frames (from the same origin so they
+    // are able to access eachother).
+    SimRequest mainResource("https://example.com/", "text/html");
+    SimRequest firstFrameResource("https://thirdparty.com/first.html", "text/html");
+    SimRequest secondFrameResource("https://thirdparty.com/second.html", "text/html");
+    loadURL("https://example.com/");
+    mainResource.complete(
+        "<iframe id=first name=first src='https://thirdparty.com/first.html'></iframe>\n"
+        "<iframe id=second name=second src='https://thirdparty.com/second.html'></iframe>");
+
+    // The first frame contains just a simple div. This frame will be made
+    // throttled.
+    firstFrameResource.complete("<div id=d>first frame</div>");
+
+    // The second page has a script which, inside a requestAnimationFrame
+    // callback, mutates the first (throttled) frame's contents and then
+    // requests a synchronous style computation of that first frame.
+    secondFrameResource.complete(
+        "<script>"
+        "window.addEventListener('load', function() {\n"
+        // Set up the rAF callback after a delay. Otherwise it will get serviced
+        // as a part of the first composition pass.
+        "  window.setTimeout(function() {\n"

[esprehn, 2016/05/19 18:53:59]

I don't think we want this delay, just run the right sequence of calls inside
the test. Ex. Composite the first frame or something. You shouldn't need to
setTimeout, your test is the scheduler.

[Sami, 2016/05/19 19:05:20]

Good point, done.

+        "    window.requestAnimationFrame(function() {\n"
+        "      var throttledFrame = window.parent.frames['first'];\n"
+        "      throttledFrame.document.documentElement.style = 'margin: 50px';\n"
+        "      throttledFrame.document.querySelector('#d').getBoundingClientRect();\n"
+        "    });\n"
+        "  }, 0);\n"
+        "});\n"
+        "</script>\n");
+
+    // Throttle the first frame.
+    auto* firstFrameElement = toHTMLIFrameElement(document().getElementById("first"));
+    firstFrameElement->setAttribute(styleAttr, "transform: translateY(480px)");
+    compositeFrame();
+    EXPECT_TRUE(firstFrameElement->contentDocument()->view()->canThrottleRendering());
+
+    // Service the requestAnimationFrame for the second frame. This should not
+    // result in an unexpected lifecycle state even if the first frame is
+    // throttled during the requestAnimationFrame callback.
+    compositeFrame();
+}
+
 } // namespace blink