Fix GrResourceCache::removeAll when one resource holds a lock on another

[bsalomon, 2011-08-19 19:01:31]

My recent change to remove createRTFrom3DAPIState exposed a latent issue in the
GrResource cache that triggered a (probably benign) assert. The issue has been
around since my stencil buffer changes went in a few weeks ago.

When the cache destroys a GrRenderTarget in GrResourceCache::removeAll it can
cause a GrStencilBuffer to be unlocked. The unlock makes a call to
GrResourceCache::purgeAsNeeded while removeAll is still in its loop up-stack.
removeAll() doesn't keep the cache in a consistent state during its eviction
loop, causing assertions to fire in the nested purge.

GrResourceCache::purgeAsNeeded is already safe against nested calls. So, my fix
is to implement removeAll using purgeAsNeeded with a null cache budget and then
assert afterwards that all entries were removed.

[bsalomon, 2011-08-22 12:56:29]

Adding Mike to review since he originally wrote what became GrResourceCache.

[Stephen White, 2011-08-22 14:07:45]

Looks good, but will leave for Mike.

[bsalomon, 2011-08-22 17:31:54]

Closed with r2147.