setViewportEnabled on InternalSettings

Added possibility to --enable-viewport from internals.settings in LayoutTests.
Currently viewport can only be tested through configurationForViewport which
makes it impossible to test certain codepaths and more complicated cases. This
CL is a pre-condition for a test in another CL I am preparing.

BUG=None

Review URL: https://chromiumcodereview.appspot.com/22747002

git-svn-id: svn://svn.chromium.org/blink/trunk@156301 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make configurationForViewport match production code

While the production code has used initial viewport width and height for
device-width and device-height, the configurationForViewport API in test builds
still used separate values for the device size. This CL removes the redundant
deviceSize in the production code and removes the device parameters from
configurationForViewport so that the tests give the same results as the
production code would do.

BUG=273649

Review URL: https://chromiumcodereview.appspot.com/23101004

git-svn-id: svn://svn.chromium.org/blink/trunk@156302 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make several DOMImplementation API arguments mandatory

Make the arguments of the following DOMImplementation API arguments mandatory:
- createDocumentType()
- createDocument()

This matches the specification:
http://dom.spec.whatwg.org/#interface-domimplementation

The arguments are already mandatory in Firefox and IE10 so the compatibility
risk should be low.

BUG=272969

Review URL: https://chromiumcodereview.appspot.com/22875013

git-svn-id: svn://svn.chromium.org/blink/trunk@156303 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve WebGL SecurityError exception messages.

We're currently writing unsuppressable console messages for
'getImageData', and have only generic error messages for 'texImage2D' and
'texSubImage2D'. This patch improves both.

BUG=152212

Review URL: https://chromiumcodereview.appspot.com/23058009

git-svn-id: svn://svn.chromium.org/blink/trunk@156304 bbb929c8-8fbe-4397-9dbb-9b2b20218538