Removing callers of the WebContents::GetRenderProcessHost() method.

WebContents::GetRenderProcessHost is an API that doesn't behave as
expected with out-of-process iframes, as multiple processes can be
associated with a single WebContents.  This CL replaces callers of this
API, so that they go through an equivalent API that explicitly selects
which frame's process is needed.

This CL was started by using an ad-hoc clang-plugin that replaced
existing callsites of WebContents::GetRenderProcessHost() with a call to
something like wc->GetMainFrame()->GetProcess().  This was followed-up
by manually adding an include of render_frame_host.h and git cl format
and git cl lint and then a self-review with small tweaks (e.g. sometimes
using a wc->GetRenderViewHost()->GetProcess() is more appropriate).

This CL was uploaded by git cl split.

R=dpapad@chromium.org

Bug: 666525
Change-Id: I7f56ede89ac9d6c72debb7fa018317539bcf8fc9
Reviewed-on: https://chromium-review.googlesource.com/689101Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505088}

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

@@ -1357,7 +1357,7 @@ void PrintPreviewHandler::UnregisterForGaiaCookieChanges() {
 
 void PrintPreviewHandler::BadMessageReceived() {
   bad_message::ReceivedBadMessage(
-      GetInitiator()->GetRenderProcessHost(),
+      GetInitiator()->GetMainFrame()->GetProcess(),
       bad_message::BadMessageReason::PPH_EXTRA_PREVIEW_MESSAGE);
 }