Remove use of private SkBlurMask.h

This also makes a use of src/core/SkTraceEventCommon.h explicit.

These are small steps toward removing Skia's src/core from
the hwui include search path.

Change-Id: I4fe843a4e44a675748bfe2cef329202eb4dab7bf
Bug: skia:13983
2 files changed