DevTools: Allow setting width/height constraints in the SplitView.

Setting constrains on width/height for the first and second elements in the SplitView.
Can be set either in pixels or in percents from the total size.
Half of these were implemented in SidebarView (and now extracted to the base class).

BUG=None
R=apavlov@chromium.org, kaznacheev@chromium.org

Review URL: https://codereview.chromium.org/18689006

git-svn-id: svn://svn.chromium.org/blink/trunk@153672 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Divest functionality from CustomElementHelpers to reduce its users.

Different parts of CustomElementHelpers were used by
CustomElementConstructorBuilder and
V8(HTML|SVG)ElementWrapperFactory. This deports the parts used by
CustomElementConstructorBuilder to clarify CustomElementHelper's
purpose: It is now exclusively about Custom Element wrapper creation.

BUG=234509

Review URL: https://chromiumcodereview.appspot.com/18245006

git-svn-id: svn://svn.chromium.org/blink/trunk@153675 bbb929c8-8fbe-4397-9dbb-9b2b20218538
The most recent version of the HTML Media Capture spec changes the `capture'
attribute from an enum to a boolean (the values that used to be passed to
the enum are now supposed to be extracted from the `accept' attribute).

For now, add a `mediaCaptureEnabled' field to WebFileChooserParams and
FileChooserSettings that coexists with the existing `capture' field while
the Chromium side of the changes is done.

R=abarth@chromium.org,eseidel@chromium.org,jochen@chromium.org
BUG=240252

Review URL: https://chromiumcodereview.appspot.com/15015006

git-svn-id: svn://svn.chromium.org/blink/trunk@153676 bbb929c8-8fbe-4397-9dbb-9b2b20218538