Create base class for common functionality of Web{Local,Remote}Frame

third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp

Index: third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp b/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
index 7f43290a4dd296830ef59a298d841897d73f9a5d..a108198a66c953d8847dbdc269ca263134d32642 100644
--- a/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
+++ b/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
@@ -108,6 +108,15 @@
 
 namespace blink {
 
+namespace {
+
+Frame* toCoreFrame(WebFrame* frame)
+{
+    return frame ? frame->toImplBase()->frame() : nullptr;

[dcheng, 2015/11/23 09:00:17]

Most locations that convert a WebFrame to a Frame don't need to care about null.
This and RemoteFrameClientImpl are the only locations that need to handle this
detail.

One alternative I considered was making a sentinel placeholder for logically
null WebFrames. This would avoid the need for the null check, but at the cost of
overloading:
  explicit operator bool() so the sentinel value tests to false
  operator==(std::nullptr_t, WebFrame*)
  operator==(WebFrame*, std::nullptr_t) so the sentinel value is considered
equivalent to nullptr

In the end, this seemed too clever and easy to accidentally break in some way,
so I ended up just going with the simple way.

+}
+
+} // namespace
+
 FrameLoaderClientImpl::FrameLoaderClientImpl(WebLocalFrameImpl* frame)
     : m_webFrame(frame)
 {