Remove wtf_ceil.

According to a post by Darin Adler [1], OSX older than SnowLeopard had the
ceil() bug. We don't support the older versions of OSX.

This CL also renames LayoutUnit::wtf_ceil and Decimal::ceiling.

[1] https://bugs.webkit.org/show_bug.cgi?id=78032#c8

BUG=

Review URL: https://codereview.chromium.org/673583002

git-svn-id: svn://svn.chromium.org/blink/trunk@184171 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [FlameChart] focus flamechart when it gets shown

There are traceviewer-compliant WASD shortcuts in FlameChart for
convenient navigation. However, they are not functional unless the
FlameChart is manually selected via mouse click on an *empty* place in
flamechart (clicks on flamechart entries send you to sources view).

The patch does two things:
- makes sidebarPane unselectable so that resizing sidebar won't grab
focus
- focuses flamechart as it gets displayed

R=pfeldman, yurys

Review URL: https://codereview.chromium.org/672553002

git-svn-id: svn://svn.chromium.org/blink/trunk@184172 bbb929c8-8fbe-4397-9dbb-9b2b20218538