Make editing/pasteboard/copy-image-with-alt-text.html independent from initial value of settings

This patch changes the test script, copy-image-with-alt-text.html, independent from initial value of settings SelectionIncludesAltImageText by explicitly set its value.

At the test script created (Blink r146835, http://src.chromium.org/viewvc/blink?view=revision&revision=146835), initial value is false, then it is changed to true at Chromium r191169, http://src.chromium.org/viewvc/chrome?view=revision&revision=191169

BUG=231865
TEST=LayoutTests/editing/pasteboard/copy-image-with-alt-text.html
R=tkent@chromium.org

Review URL: https://codereview.chromium.org/23591023

git-svn-id: svn://svn.chromium.org/blink/trunk@157098 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Have RenderView's enclosingSeamlessRenderer() take a Document reference in argument

Have RenderView's enclosingSeamlessRenderer() take a Document reference in argument
instead of a pointer since the document can never be NULL. This avoids having to
convert a reference into a pointer at the call sites and gets rid of a useless
null-check.

BUG=281400

Review URL: https://chromiumcodereview.appspot.com/23533013

git-svn-id: svn://svn.chromium.org/blink/trunk@157099 bbb929c8-8fbe-4397-9dbb-9b2b20218538