Add Frame::isMainFrame and deploy it

Add Frame::isMainFrame and deploy it

I originally started this to remove Page.h includes
but found that it just made the code simpler to read in most cases.

In an out of process iframes enabled Blink it will not be
possible to access the Page object from core/, so Frame will
have to know itself if it is (or thinks it is) the main frame.

There are quite a few uses of Page::mainFrame() in core/inspector/
code but it's not obvious that the frame being compared always has
the same page as the page its being compared with, so I didn't
change those for now.

BUG=305811
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=161367

[abarth-chromium, 2013-11-05 15:57:51]

isMainView  ->  isMainFrame

It looks like you used isMainFrame in the code.

[abarth-chromium, 2013-11-05 15:59:25]

lgtm

[eseidel, 2013-11-05 18:57:04]

Yeah, sorry.  Coding at 2am my brain was shot.

[commit-bot: I haz the power, 2013-11-05 18:57:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/eseidel@chromium.org/59573002/1

[commit-bot: I haz the power, 2013-11-05 20:50:05]

Change committed as 161367