WebInputEventConversion shouldn't use bloatedCharacters

This CL uses our new copyTo technology to avoid calling bloatedCharacters.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/18272008

git-svn-id: svn://svn.chromium.org/blink/trunk@153374 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rebaselining following layout tests:
compositing/scaling/tiled-layer-recursion.html
compositing/culling/tile-occlusion-boundaries.html

R=esprehn@chromium.org
BUG=255667

Review URL: https://codereview.chromium.org/18402002

git-svn-id: svn://svn.chromium.org/blink/trunk@153376 bbb929c8-8fbe-4397-9dbb-9b2b20218538