Fix a resource race bug in PathCache

When enabled defer rendering, it will do precache for DrawPathOp.
The paint used for creating PathTask in precache just get the address
of mFilteredPaint of OpenGLRenderer. So for the following defer
operation like DrawTextOp has possibility change the mFilteredPaint
by getPaint while another WorkerThread in PathCache is using the paint
which pointed to the same address of mFilteredPaint to generate bitmap.
As a result, it will generate a wrong bitmap for generateTexture in
PathCache. To fix it, do a copy of paint when creating PathTask.

CRs-Fixed: 664244

Change-Id: I5516f5b143458b88d3573d15b7ebb34f688800c7