DevTools: trim whitespaces from devtools css files

This patch trims all whitespaces from devtools css files, which saves 12Kb of space on Linux.

R=apavlov

Review URL: https://codereview.chromium.org/825623003

git-svn-id: svn://svn.chromium.org/blink/trunk@187678 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [SSP] inherit ComputedStyleSidebarPane from ElementsSidebarPane

The patch inherits ComputedStyleSidebarPane from ElementsSidebarPane,
thus drastically simplifying code from both StylesSidebarPane and and
ComputedStylesSidebarPane.

With this change, the SSP._refreshUpdate becomes synchronous - there's
no more need to fetch computed style for CSSP, it handles it on its own.

R=vsevik

Review URL: https://codereview.chromium.org/810253003

git-svn-id: svn://svn.chromium.org/blink/trunk@187681 bbb929c8-8fbe-4397-9dbb-9b2b20218538