Add Tracing.getCategories to protocol.json.

BUG=

Review URL: https://codereview.chromium.org/331303002

git-svn-id: svn://svn.chromium.org/blink/trunk@176439 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Qualify RuntimeEnabledFeatures.h and remove unnecessary include dir.

This CL removes the gen/blink/platform dir in core.gyp and qualifies
all the instances that include RuntimeEnabledFeatures.h.

BUG=381876

Review URL: https://codereview.chromium.org/344593002

git-svn-id: svn://svn.chromium.org/blink/trunk@176440 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Round in the range [-0.5, 0.5) when computing offsetFromRenderer and subpixelAccumulation
for squashed layers.

Also remove the assert that the subpixel accumulation matches
the subpixel accumulation if the layer was separately
composited. This doesn't make sense, since the squashing
layer is positioned relative to the compositing ancestor
of m_owningLayer, not the squashing layer, which can have
different subpixel accumulations since subpixel
accumulation is relative to the compositing container of
the graphics layer.

BUG=369526

Review URL: https://codereview.chromium.org/343543005

git-svn-id: svn://svn.chromium.org/blink/trunk@176441 bbb929c8-8fbe-4397-9dbb-9b2b20218538