Use FrameMatchingPredicate() to find RenderFrameHosts in ExtensionWebUITest.

When looking for a RFH by last committed URL, there is no need to do a ForEach with a private FindFrame() predicate, since that logic is already available from a public FrameMatchingPredicate method in browser_test_utils.

BUG=

Review URL: https://codereview.chromium.org/807463003

Cr-Commit-Position: refs/heads/master@{#308458}

chrome/browser/extensions/extension_webui_apitest.cc

@@ -26,17 +26,6 @@ namespace OnMessage = core_api::test::OnMessage;
 
 namespace {
 
-void FindFrame(const GURL& url,
-               content::RenderFrameHost** out,
-               content::RenderFrameHost* frame) {
-  if (frame->GetLastCommittedURL() == url) {
-    if (*out != NULL) {
-      ADD_FAILURE() << "Found multiple frames at " << url;
-    }
-    *out = frame;
-  }
-}
-
 // Tests running extension APIs on WebUI.
 class ExtensionWebUITest : public ExtensionApiTest {
  protected:
@@ -119,10 +108,9 @@ class ExtensionWebUITest : public ExtensionApiTest {
     if (active_web_contents->GetLastCommittedURL() == frame_url)
       return active_web_contents->GetMainFrame();
 
-    content::RenderFrameHost* frame_host = NULL;
-    active_web_contents->ForEachFrame(
-        base::Bind(&FindFrame, frame_url, &frame_host));
-    return frame_host;
+    return FrameMatchingPredicate(
+        active_web_contents,
+        base::Bind(&content::FrameHasSourceUrl, frame_url));
   }
 };