Merge FontPlatformDataHarfBuzz into FontPlatformData

From WebKit legacy we have two redundant copies of this file.
In order for switching shapers on mac, we need to fuse these files again.
This is part two of the merge,
after the headers were merged in r181655 / ad011a9df.

This is a re-land after the original patch got reverted
in 9ebff84df32cb645b6 due to uninitialized memory, reported in bug 413229.
Now changed: Initialized m_widthVariant in SkTypeface FontPlatformData constructor,
reshuffle windows initializers in the right order, and
added m_isHashTableDeletedValue to the Skia hash function.

BUG=334269,413229
R=eae

Review URL: https://codereview.chromium.org/568393003

git-svn-id: svn://svn.chromium.org/blink/trunk@182111 bbb929c8-8fbe-4397-9dbb-9b2b20218538