Use Blink support to watch CSS selectors directly instead of using a MutationObserver.

chrome/browser/extensions/api/declarative_content/declarative_content_apitest.cc

 // Copyright (c) 2012 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 "chrome/browser/extensions/extension_action.h"
 #include "chrome/browser/extensions/extension_action_manager.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/extensions/extension_test_message_listener.h"
 #include "chrome/browser/extensions/test_extension_dir.h"
@@ skipping 78 matching lines @@
   // than waiting for the extension to run.
   EXPECT_TRUE(page_action->GetIsVisible(tab_id));
 
   // Make sure leaving a matching page unshows the page action.
   NavigateInRenderer(tab, GURL("http://not_checked/"));
   EXPECT_FALSE(page_action->GetIsVisible(tab_id));
 
   // Insert a password field to make sure that's noticed.
   ASSERT_TRUE(content::ExecuteScript(
       tab, "document.body.innerHTML = '<input type=\"password\">';"));
-  // Give the mutation observer a chance to run and send back the
-  // matching-selector update.
+  // Give the style match a chance to run and send back the matching-selector
+  // update.  This takes one time through the Blink message loop to apply the
+  // style to the new element, and a second to dedupe updates.
+  ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
   ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
   EXPECT_TRUE(page_action->GetIsVisible(tab_id))
       << "Adding a matching element should show the page action.";
 
   // Remove it again to make sure that reverts the action.
   ASSERT_TRUE(content::ExecuteScript(
       tab, "document.body.innerHTML = 'Hello world';"));
-  // Give the mutation observer a chance to run and send back the
-  // matching-selector update.
+  // Give the style match a chance to run and send back the
+  // matching-selector update.  This also takes 2 iterations.
+  ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
   ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
   EXPECT_FALSE(page_action->GetIsVisible(tab_id))
       << "Removing the matching element should hide the page action again.";
 }
 
 // This tests against a renderer crash that was present during development.
 IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest,
                        AddExtensionMatchingExistingTabWithDeadFrames) {
   ext_dir_.WriteManifest(kDeclarativeContentManifest);
   ext_dir_.WriteFile(
@@ skipping 28 matching lines @@
 
   EXPECT_EQ("rule0",
             ExecuteScriptInBackgroundPage(
                 extension->id(),
                 "setRules([{\n"
                 "  conditions: [new PageStateMatcher({\n"
                 "                   css: [\"span[class=foo]\"]})],\n"
                 "  actions: [new ShowPageAction()]\n"
                 "}], 'rule0');\n"));
   // Give the renderer a chance to apply the rules change and notify the
-  // browser.
+  // browser.  This takes one time through the Blink message loop to receive
+  // the rule change and apply the new stylesheet, and a second to dedupe the
+  // update.
+  ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
   ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
 
   EXPECT_FALSE(tab->IsCrashed());
   EXPECT_TRUE(page_action->GetIsVisible(tab_id))
       << "Loading an extension when an open page matches its rules "
       << "should show the page action.";
 
   EXPECT_EQ("removed",
             ExecuteScriptInBackgroundPage(
                 extension->id(),
@@ skipping 57 matching lines @@
                   "  new PageStateMatcher({css: ['div input']});\n"
                   "  Return('Failed to throw');\n"
                   "} catch (e) {\n"
                   "  Return(e.message);\n"
                   "}\n"),
               testing::ContainsRegex("compound selector.*: div input$"));
 }
 
 }  // namespace
 }  // namespace extensions