Move [StrictTypeChecking] to interface (from members), where possible

No changes to generated bindings: just simplification.

kouhei:
there's one case in an SVG IDL that might need fixing,
namely createSVGTransformFromMatrix in
Source/core/svg/SVGSVGElement.idl
(only case of an SVG method not having [StrictTypeChecking]
when others on the interface do)

[StrictTypeChecking] is almost always applied to all members of an interface.
Thus it's clearer and safer to put in on the interface, instead of the members.
This requires minimal CG changes (just check [StrictTypeChecking] on interface),
and allows *massive* simplification of IDL files.

This is ultimately in support of the SVG bindings rewrite,
as we want strict type checking there for null.

There are only 3 IDL files left with [StrictTypeChecking] on members:
(outside of test cases)
* Source/core/html/HTMLMediaElement.idl
* Source/core/svg/SVGSVGElement.idl  ::  kouhei?
* Source/modules/mediastream/RTCPeerConnection.idl

Also some formatting fixes to WebGLRenderingContext.idl,
which is v. long and was quite inconsistent.
(And a few to SVGPathElement.idl, due to long argument lists.)

Followup to:
Add null-correctness checking to [StrictTypeChecking] methods
https://codereview.chromium.org/141523002/

BUG=249598
R=haraken

Review URL: https://codereview.chromium.org/146423002

git-svn-id: svn://svn.chromium.org/blink/trunk@165749 bbb929c8-8fbe-4397-9dbb-9b2b20218538