FrameView: Remove redundant tree walk when unthrottling display:none frames

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 "bindings/core/v8/ScriptController.h"
 #include "bindings/core/v8/ScriptSourceCode.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 1033 matching lines @@
   // Initially the frame is throttled as it is offscreen.
   compositeFrame();
   EXPECT_TRUE(frameDocument->view()->canThrottleRendering());
 
   // Setting display:none unthrottles the frame.
   frameElement->setAttribute(styleAttr, "display: none");
   compositeFrame();
   EXPECT_FALSE(frameDocument->view()->canThrottleRendering());
 }
 
+TEST_P(FrameThrottlingTest, DisplayNoneChildrenRemainThrottled) {
+  // Create two nested frames which are throttled.
+  SimRequest mainResource("https://example.com/", "text/html");
+  SimRequest frameResource("https://example.com/iframe.html", "text/html");
+  SimRequest childFrameResource("https://example.com/child-iframe.html",
+                                "text/html");
+
+  loadURL("https://example.com/");
+  mainResource.complete("<iframe id=frame sandbox src=iframe.html></iframe>");
+  frameResource.complete(
+      "<iframe id=child-frame sandbox src=child-iframe.html></iframe>");
+  childFrameResource.complete("");
+
+  // Move both frames offscreen to make them throttled.
+  auto* frameElement = toHTMLIFrameElement(document().getElementById("frame"));
+  auto* childFrameElement = toHTMLIFrameElement(
+      frameElement->contentDocument()->getElementById("child-frame"));
+  frameElement->setAttribute(styleAttr, "transform: translateY(480px)");
+  compositeFrame();
+  EXPECT_TRUE(frameElement->contentDocument()->view()->canThrottleRendering());
+  EXPECT_TRUE(
+      childFrameElement->contentDocument()->view()->canThrottleRendering());
+
+  // Setting display:none for the parent frame unthrottles the parent but not
+  // the child. This behavior matches Safari.
+  frameElement->setAttribute(styleAttr, "display: none");
+  compositeFrame();
+  EXPECT_FALSE(frameElement->contentDocument()->view()->canThrottleRendering());
+  EXPECT_TRUE(
+      childFrameElement->contentDocument()->view()->canThrottleRendering());
+}
+
 }  // namespace blink