Create cache identity from GL_VERSION and store in ShaderCache.
In the next time ShaderCache is restored from disk, compare the
cache identity to ensure its validity. If GL_VERSION changes in
between, flush out entire FileBlobCache and start from an empty
one.
Bug: b/71800782
Test: Wrote a new unit test to save and restore ShaderCache
Test: hwui_unit_tests
Change-Id: Ie573dc4f18733eee090725be30445d879765231b
Implement SkSL cache by reusing code and logic from egl_cache_t.
Test: Improves startup times for gmail by 15ms and 10ms for calc app.
Bug: 66740665
Change-Id: I9ba479c649ba97a2c29a48d40579ba001264c957