Use WebBlendMode in FEBlend

This replaces the BlendModeType enumeration with the WebBlendMode for
FEBlend::m_mode. The former is moved to SVGFEBlendElement.
This enables FEBlend to use all of the blend modes available in
WebBlendMode, and leave any subset selection to the client of FEBlend
(which is SVGFEBlendElement).
The BlendModeType->string mapping is replaced by compositeOperatorName().

BUG=389594

Review URL: https://codereview.chromium.org/419253002

git-svn-id: svn://svn.chromium.org/blink/trunk@179029 bbb929c8-8fbe-4397-9dbb-9b2b20218538
HTMLImageElement.natural{Width,Height} should return intrinsic dimensions

HTML says:

 "The IDL attributes naturalWidth and naturalHeight must return the
  intrinsic width and height of the image, in CSS pixels, if the image is
  available, or else 0."

Change HTMLImageElement::natural{Width,Height} to request the intrinsic
size from ImageResource::imageSizeForRenderer by passing IntrinsicSize as
the third parameter. This makes the attributes return more appropriate
values for SVG-images in <img>.

BUG=396955

Review URL: https://codereview.chromium.org/422503002

git-svn-id: svn://svn.chromium.org/blink/trunk@179030 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [Elements] Implement shortcut-based node cut-copy-pasting

R=aandrey, pfeldman, vsevik
BUG=394384

Review URL: https://codereview.chromium.org/397303002

git-svn-id: svn://svn.chromium.org/blink/trunk@179031 bbb929c8-8fbe-4397-9dbb-9b2b20218538