Added ability to flush context to GrTextBlobCache

The TextBlobCache needs the ability to trigger a flush because otherwise its entire budget can be used up, but it will not be able to free up any space due to blobs being stuck in the GrInOrderDrawBuffer.  This was causing a segfault.  After this CL the cache will try to purge, and then flush if it cannot purge enough.  It will not purge the most recent addition to the cache.

TBR=bsalomon@google.com
BUG=skia:

Committed: https://skia.googlesource.com/skia/+/0db6dfaeb2d1376ad393516fb22af7ecf62718fa

[joshualitt, 2015-04-09 21:44:57]

joshualitt@google.com changed reviewers:
+ joshualitt@google.com, robertphillips@google.com

[joshualitt, 2015-04-09 21:44:58]

ptal

[robertphillips, 2015-04-10 12:22:46]

lgtm + nits. Could you expand the CL description to include what's going on/why
this is necessary?

https://codereview.chromium.org/1071333002/diff/20001/src/gpu/GrContext.cpp
File src/gpu/GrContext.cpp (right):

https://codereview.chromium.org/1071333002/diff/20001/src/gpu/GrContext.cpp#n...
src/gpu/GrContext.cpp:360: GrContext* context =
reinterpret_cast<GrContext*>(data);
// Words here about why just flushing rather than setting the
'fFlushToReduceCacheSize' flag ?

https://codereview.chromium.org/1071333002/diff/20001/src/gpu/GrTextBlobCache.h
File src/gpu/GrTextBlobCache.h (right):

https://codereview.chromium.org/1071333002/diff/20001/src/gpu/GrTextBlobCache...
src/gpu/GrTextBlobCache.h:79: 
use an "#ifdef SK_DEBUG/#endif" block for this rather than a multiline
SkDEBUGCODE?

[joshualitt, 2015-04-10 13:18:55]

The CQ bit was checked by joshualitt@google.com

[joshualitt, 2015-04-10 13:18:55]

The patchset sent to the CQ was uploaded after l-g-t-m from
robertphillips@google.com
Link to the patchset: https://codereview.chromium.org/1071333002/#ps40001
(title: "feedback inc")

[commit-bot: I haz the power, 2015-04-10 13:19:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1071333002/40001

[commit-bot: I haz the power, 2015-04-10 13:19:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-10 13:19:13]

Presubmit check for 1071333002-40001 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com', 'djsollen@chromium.org', 'djsollen@google.com')

[joshualitt, 2015-04-10 13:22:35]

joshualitt@google.com changed reviewers:
+ bsalomon@google.com

[joshualitt, 2015-04-10 13:53:39]

The CQ bit was checked by joshualitt@google.com

[joshualitt, 2015-04-10 13:53:51]

The CQ bit was unchecked by joshualitt@google.com

[commit-bot: I haz the power, 2015-04-10 13:53:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1071333002/40001

[commit-bot: I haz the power, 2015-04-10 13:54:00]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-10 13:54:01]

Presubmit check for 1071333002-40001 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com', 'djsollen@chromium.org', 'djsollen@google.com')

Was the presubmit check useful? If not, run "git cl presubmit -v"
to figure out which PRESUBMIT.py was run, then run git blame
on the file to figure out who to ask for help.

[joshualitt, 2015-04-10 13:54:10]

The CQ bit was checked by joshualitt@google.com

[commit-bot: I haz the power, 2015-04-10 13:54:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1071333002/40001

[commit-bot: I haz the power, 2015-04-10 14:01:34]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/0db6dfaeb2d1376ad393516fb22af7ecf62718fa