DevTools: add more jsdocs to NetworkPanel.

BUG=

Review URL: https://codereview.chromium.org/352983004

git-svn-id: svn://svn.chromium.org/blink/trunk@177075 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Fix UI extreme cases: very small window and very large zoom.

BUG=388185

Review URL: https://codereview.chromium.org/342683008

git-svn-id: svn://svn.chromium.org/blink/trunk@177076 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL: Remove a FIXME comment for using local variables

Using local variable for isolate in attribute_getter will add
complexity and won't pay for it.

BUG=345503

Review URL: https://codereview.chromium.org/359703002

git-svn-id: svn://svn.chromium.org/blink/trunk@177077 bbb929c8-8fbe-4397-9dbb-9b2b20218538