DevTools: switch devtools platform events to new timeline category

This switches trace events emitted from PlatformInstrumentation to use
trace event category consistent with the trace-based timeline.
Drive-by: fix category filter in TraceEventDispatcher.

BUG=361045

Review URL: https://codereview.chromium.org/337143002

git-svn-id: svn://svn.chromium.org/blink/trunk@176413 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Timeline: show record details as a tabbed pane

This changes TimelineDetailsView to be a TabbedPane and lets us add
additional tabs for record types where we can show more details (e.g.
layer tree view or paint profiler). The old details remain in "default"
first tab. Also, for selected range stats, we now show range begin-end
as a part of details view, not in the header.

BUG=

Review URL: https://codereview.chromium.org/325313006

git-svn-id: svn://svn.chromium.org/blink/trunk@176414 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: fix MediaController crashes after r176358.

MediaController::trace() needs to have the declaration of ExecutionContext
available, so as to determine what NeedsAdjustAndMark<> resolves to for
its (weak) ExecutionContext member.

R=haraken@chromium.org,zerny@chromium.org
BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/344443008

git-svn-id: svn://svn.chromium.org/blink/trunk@176415 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Word spacing in RTL for segments

Removed m_stop and length comparison as they carry different units i.e. if there are two char text then m_stop will be 1 and length 2. As do not compare, needWordSpace does not set correct value.  

Also by default condition for needSpacing has been changed to true because if first character is space it was getting omitted. 

BUG=344873
R=leviw, eae
TEST=Word spacing in RTL with different segments handling.

Review URL: https://codereview.chromium.org/343443002

git-svn-id: svn://svn.chromium.org/blink/trunk@176416 bbb929c8-8fbe-4397-9dbb-9b2b20218538