Remove code guarded by never-ENABLED defines

The enable flags in question are:
  - COMPARE_AND_SWAP
  - HIGH_DPI_CANVAS
  - IMAGE_DECODER_DOWN_SAMPLING

Also removed some other unused code in wtf/Atomics.h

R=abarth

Review URL: https://chromiumcodereview.appspot.com/5741031244955648

git-svn-id: svn://svn.chromium.org/blink/trunk@154058 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove generic TextFieldDecorator in favor of PasswordGeneratorButtonElement

The generic support for text field decorators is only used by password generator
icons and also prevents us from allowing author ShadowRoots on <input>'s. It's
also not clear that we ever want to really allow lots of little icons inside inputs,
currently we'd allow 8 of them, but that seems crazy to stuff into inputs.

This is the first step of tightening up the interface for password generator just like
SpeechInputClient and allows removing 300 lines of code.

R=tkent@chromium.org

Review URL: https://codereview.chromium.org/18414005

git-svn-id: svn://svn.chromium.org/blink/trunk@154059 bbb929c8-8fbe-4397-9dbb-9b2b20218538
document.body getter/setter should match the HTML5 spec

Document::setBody previously would create a deep copy of the node if you moved it
from a different document and didn't allow framesets. Document::body would incorrectly
return <frameset> even if <body> came first. I also made setBody AttachLazily just
like doing appendChild(body) would have done.

Spec: http://www.whatwg.org/specs/web-apps/current-work/multipage/dom.html#dom-document-body

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/5645889129414656

git-svn-id: svn://svn.chromium.org/blink/trunk@154060 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Prevent fast/canvas/webgl/read-pixels-test.html from timing out.

Reduce the amount of rendering the test does in order to keep it from timing out. The remainder of the test still provides some useful coverage.

BUG=259069
R=ojan@chromium.org

Review URL: https://chromiumcodereview.appspot.com/18161005

git-svn-id: svn://svn.chromium.org/blink/trunk@154061 bbb929c8-8fbe-4397-9dbb-9b2b20218538