IDL compiler: sync Python to CL 26985002

activeScriptExecutionContext => activeExecutionContext

Rename ScriptExecutionContext to ExecutionContext.
https://codereview.chromium.org/26985002

NOTRY=true

Review URL: https://codereview.chromium.org/26591005

git-svn-id: svn://svn.chromium.org/blink/trunk@159628 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Don't call didRecalcStyle or willRecalcStyle unless we really did

Instead of calling these methods as we walk down the tree and back up
during a style recalc only call them if the element's style really was
recalculated. This should save a few virtual calls in html pages, but
will save thousands in SVG documents since SVGElement (the base class
for svg) sets itself as needing custom style callbacks.

Review URL: https://codereview.chromium.org/26634004

git-svn-id: svn://svn.chromium.org/blink/trunk@159629 bbb929c8-8fbe-4397-9dbb-9b2b20218538