Fixing memory leak in RenderBufferCache

In our devices with higher resolution we have observed a memory
leak in the HWUI code. When there is GC or tree modification
and buffer size is greater than the default size, we make sure
buffer is deleted.

Change-Id: Idf7052ccaf43c8a784ce0e7bdab336dca29bffd8
Signed-off-by: Samsung <aosp@samsung.com>