TestRunner: add method to instrument autoplay settings and set default value.

components/test_runner/mock_content_settings_client.cc

Index: components/test_runner/mock_content_settings_client.cc
diff --git a/components/test_runner/mock_content_settings_client.cc b/components/test_runner/mock_content_settings_client.cc
index 6bcee665f4b851484e0866d617cc035cc1c61619..4aa8c004314369c97fbb3bb83afc25a86a9ba37a 100644
--- a/components/test_runner/mock_content_settings_client.cc
+++ b/components/test_runner/mock_content_settings_client.cc
@@ -21,9 +21,10 @@ bool MockContentSettingsClient::allowImage(bool enabled_per_settings,
                                            const blink::WebURL& image_url) {
   bool allowed = enabled_per_settings && flags_->images_allowed();
   if (flags_->dump_web_content_settings_client_callbacks() && delegate_) {
-    delegate_->PrintMessage(std::string("PERMISSION CLIENT: allowImage(") +
-                            NormalizeLayoutTestURL(image_url.string().utf8()) +
-                            "): " + (allowed ? "true" : "false") + "\n");
+    delegate_->PrintMessage(
+        std::string("MockContentSettingsClient: allowImage(") +
+        NormalizeLayoutTestURL(image_url.string().utf8()) +
+        "): " + (allowed ? "true" : "false") + "\n");
   }
   return allowed;
 }
@@ -31,9 +32,10 @@ bool MockContentSettingsClient::allowImage(bool enabled_per_settings,
 bool MockContentSettingsClient::allowMedia(const blink::WebURL& image_url) {
   bool allowed = flags_->media_allowed();
   if (flags_->dump_web_content_settings_client_callbacks() && delegate_)
-    delegate_->PrintMessage(std::string("PERMISSION CLIENT: allowMedia(") +
-                            NormalizeLayoutTestURL(image_url.string().utf8()) +
-                            "): " + (allowed ? "true" : "false") + "\n");
+    delegate_->PrintMessage(
+        std::string("MockContentSettingsClient: allowMedia(") +
+        NormalizeLayoutTestURL(image_url.string().utf8()) +
+        "): " + (allowed ? "true" : "false") + "\n");
   return allowed;
 }
 
@@ -43,7 +45,7 @@ bool MockContentSettingsClient::allowScriptFromSource(
   bool allowed = enabled_per_settings && flags_->scripts_allowed();
   if (flags_->dump_web_content_settings_client_callbacks() && delegate_) {
     delegate_->PrintMessage(
-        std::string("PERMISSION CLIENT: allowScriptFromSource(") +
+        std::string("MockContentSettingsClient: allowScriptFromSource(") +
         NormalizeLayoutTestURL(scriptURL.string().utf8()) + "): " +
         (allowed ? "true" : "false") + "\n");
   }
@@ -71,6 +73,10 @@ bool MockContentSettingsClient::allowRunningInsecureContent(
   return enabled_per_settings || flags_->running_insecure_content_allowed();
 }
 
+bool MockContentSettingsClient::allowAutoplay(bool defaultValue) {
+  return defaultValue || flags_->autoplay_allowed();
+}
+
 void MockContentSettingsClient::SetDelegate(WebTestDelegate* delegate) {
   delegate_ = delegate;
 }