Add null check when accessing WebLocalFrameImpl::mainFrameImpl().

The main frame might be null, so we need to check that before trying to
dereference it to see if it's a local frame.

BUG=385162

Review URL: https://codereview.chromium.org/334323002

git-svn-id: svn://svn.chromium.org/blink/trunk@176245 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Mark inspector-protocol/stylesheet-tracking-restart.html as flaky after r176213.

TBR=vsevik@chromium.org
BUG=354447

Review URL: https://codereview.chromium.org/331313002

git-svn-id: svn://svn.chromium.org/blink/trunk@176246 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove inefficiency from HTMLCollection::namedItems()

Remove inefficiency from HTMLCollection::namedItems(). The code was
unnecessarily checking that the pointers were non-null for every iteration of
the for loops. This CL updates the code so that the null check is done only
once.

R=esprehn@chromium.org, adamk@chromium.org

Review URL: https://codereview.chromium.org/337963002

git-svn-id: svn://svn.chromium.org/blink/trunk@176247 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make Ctor/Dtor of ExecutionContext protected.

BUG=305497

Review URL: https://codereview.chromium.org/328263003

git-svn-id: svn://svn.chromium.org/blink/trunk@176248 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add support in generate scripts to handle Conditional

WEB_AUDIO and SVG_FONTS conditions in tagName files were 
handled by generate scripts and this CL adds the support. 
This fix was also needed to build without SVG_FONTS enabled.

Review URL: https://codereview.chromium.org/330093002

git-svn-id: svn://svn.chromium.org/blink/trunk@176249 bbb929c8-8fbe-4397-9dbb-9b2b20218538