Add share button to generate public url for dmprof visualizer.

User now can click share button to generate a public url for current breakdown
template. Url will be shown next to the share button.

Also make some trivial improvements on GUI.

BUG=259206
NOTRY=True

Review URL: https://codereview.chromium.org/24534002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225308 0039d316-1c4b-4281-b951-d872f2087c98