Cleanup: Add more conversion helpers for usage.

Source/web/FrameLoaderClientImpl.h

Index: Source/web/FrameLoaderClientImpl.h
diff --git a/Source/web/FrameLoaderClientImpl.h b/Source/web/FrameLoaderClientImpl.h
index 945c8c38fa317bb3d993a806a927c1a09cab9665..a4214285eaf01a52cd26cefde6226bcaf6bbe81d 100644
--- a/Source/web/FrameLoaderClientImpl.h
+++ b/Source/web/FrameLoaderClientImpl.h
@@ -163,6 +163,14 @@ private:
     WebFrameImpl* m_webFrame;
 };
 
+inline FrameLoaderClientImpl* toFrameLoaderClientImpl(WebCore::FrameLoaderClient* client)
+{
+    // We need not check for type of FrameLoaderClient since FrameLoaderClientImpl
+    // is the only derived class of FrameLoaderClient.
+    ASSERT_WITH_SECURITY_IMPLICATION(!client);

[tkent, 2013/10/08 05:24:04]

Null pointer has no security implication.
Please do not reject null client for consistency.

+    return static_cast<FrameLoaderClientImpl*>(client);
+}
+
 } // namespace WebKit
 
 #endif