Add trace events to HTMLDocumentParser to try capturing uncategorized time. This is part of an effort to identify what contributes to the ~12.6% "uncategorized" time from the android top 25k experiment. For sites high in uncategorized time, this accounts for about ~6% of the trace. 

BUG=

Review URL: https://codereview.chromium.org/26110005

git-svn-id: svn://svn.chromium.org/blink/trunk@159262 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Moving all the PlatformEvent subclasses from core/platform to platform

BUG=297477

Review URL: https://codereview.chromium.org/26510003

git-svn-id: svn://svn.chromium.org/blink/trunk@159263 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[SVG] Remove a couple of redundant hashmap look-ups.

No need for a separate contains() check - HashMap remove/take can handle
missing elements just fine.

R=pdr@chromium.org,schenney@chromium.org

Review URL: https://codereview.chromium.org/26725002

git-svn-id: svn://svn.chromium.org/blink/trunk@159264 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Clean up old comments related to custom Node insertBefore etc

BUG=None

Review URL: https://codereview.chromium.org/26567005

git-svn-id: svn://svn.chromium.org/blink/trunk@159265 bbb929c8-8fbe-4397-9dbb-9b2b20218538