Reload devtools extensions when devtools are reloaded

BUG=306267

Review URL: https://codereview.chromium.org/44523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231052 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231052
Device monitor Mac bug corrected when removing audio.

Silly typo made it test twice for video removal :(

Please refer to bug for details on testing.

BUG=311255

Review URL: https://codereview.chromium.org/43633002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231053 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231053