Fix RenderBlock::percentHeightDescendants()

RenderBlock::percentHeightDescendants() is used to schedule layout of
descencents of a block when the logical height of the block changes.
It should contain descendants having percent height whose real height
calculation depends on the height of the block.

Previously
- the set doesn't contain direct children;
- skipped containing blocks for percent height calculation unnecessarily
  have the set.

Let the set contain all necessary objects. This doesn't fix any
functional breakage for now, but later layout optimization may depend
on the correct behavior of the function.

BUG=327815
TEST=WebFrameTest.RenderBlockPercentHeightDescendants

Review URL: https://codereview.chromium.org/201153008

git-svn-id: svn://svn.chromium.org/blink/trunk@169588 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add isHTMLPlugInElement() helpers for consistency with other HTML elements

Add isHTMLPlugInElement() helpers for consistency with other HTML elements.
Those helpers rely on the isPluginElement() virtual function to check if
an Element is an HTMLPlugInElement.

R=tkent, adamk
BUG=346095

Review URL: https://codereview.chromium.org/202153005

git-svn-id: svn://svn.chromium.org/blink/trunk@169589 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add WebSerializedOrigin to represent a serialized Web Origin.

Use it in WebSocket.

BUG=339373
R=tyoshino, abarth

Review URL: https://codereview.chromium.org/201593002

git-svn-id: svn://svn.chromium.org/blink/trunk@169591 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Implement font-family: initial.

It appears that this never worked correctly. To implement,
I extracted the code we use to set initial value for document and
started using it when applying initial font-family value.

BUG=354110
R=eseidel,eae

Review URL: https://codereview.chromium.org/197213034

git-svn-id: svn://svn.chromium.org/blink/trunk@169592 bbb929c8-8fbe-4397-9dbb-9b2b20218538