WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

content/browser/webui/web_ui_impl.cc

Index: content/browser/webui/web_ui_impl.cc
diff --git a/content/browser/webui/web_ui_impl.cc b/content/browser/webui/web_ui_impl.cc
index c4c5b63306701f475c23d9a1c463bd1c2d60a6f2..41fc037852c786645705881beed7ad9ca6d0e0fa 100644
--- a/content/browser/webui/web_ui_impl.cc
+++ b/content/browser/webui/web_ui_impl.cc
@@ -144,6 +144,16 @@ void WebUIImpl::SetController(WebUIController* controller) {
   controller_.reset(controller);
 }
 
+bool WebUIImpl::CanCallJavascript() {
+  RenderFrameHost* target_frame = TargetFrame();
+  return target_frame &&
+         (ChildProcessSecurityPolicyImpl::GetInstance()->HasWebUIBindings(
+              target_frame->GetProcess()->GetID()) ||
+          // It's possible to load about:blank in a Web UI renderer.
+          // See http://crbug.com/42547
+          target_frame->GetLastCommittedURL().spec() == url::kAboutBlankURL);
+}
+
 void WebUIImpl::CallJavascriptFunction(const std::string& function_name) {
   DCHECK(base::IsStringASCII(function_name));
   base::string16 javascript = base::ASCIIToUTF16(function_name + "();");
@@ -233,19 +243,12 @@ void WebUIImpl::AddMessageHandler(WebUIMessageHandler* handler) {
 }
 
 void WebUIImpl::ExecuteJavascript(const base::string16& javascript) {
-  RenderFrameHost* target_frame = TargetFrame();
-  if (target_frame) {
-    if (!(ChildProcessSecurityPolicyImpl::GetInstance()->HasWebUIBindings(
-              target_frame->GetProcess()->GetID()) ||
-          // It's possible to load about:blank in a Web UI renderer.
-          // See http://crbug.com/42547
-          target_frame->GetLastCommittedURL().spec() == url::kAboutBlankURL)) {
-      // Silently ignore the request. Would be nice to clean-up WebUI so we
-      // could turn this into a CHECK(). http://crbug.com/516690.
-      return;
-    }
-    target_frame->ExecuteJavaScript(javascript);
-  }
+  // Silently ignore the request. Would be nice to clean-up WebUI so we
+  // could turn this into a CHECK(). http://crbug.com/516690.
+  if (!CanCallJavascript())
+    return;
+
+  TargetFrame()->ExecuteJavaScript(javascript);
 }
 
 RenderFrameHost* WebUIImpl::TargetFrame() {