Remove old WebSourceBufferImpl::append()

This is the third part of a three-sided MediaSource
Chromium/Blink+roll Blink/Chromium set of changes to enable
JavaScript web apps to continue to round-trip
SourceBuffer.timestampOffset set/get if SourceBuffer append
operations do not update the timestamp offset, and to
retrieve any updated timestamp offset as can occur during
upcoming "sequence" append mode compliant coded frame
processing.

This change removes the obsolete Chromium
WebSourceBufferImpl::append(,) now that Blink
WebSourceBuffer.h only has append(,,double*).

R=acolwell@chromium.org
BUG=249422
TEST=All media_unittests and http/tests/media/media-source layout tests pass locally on Linux

Review URL: https://codereview.chromium.org/183933002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255373 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255373
Suppress memory issue in MachineStatisticsInitializer

BUG=349948
TBR=dpolukhin@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/184243004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255374 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255374