Revert of By default purge resources that haven't been used for 64 flushes (patchset #5 id:80001 of https://codereview.chromium.org/1316233003/ )

Reason for revert:
Breaking conformance test again

Original issue's description:
> By default purge resources that haven't been used for 64 flushes
>
> BUG=skia:4258
>
> Committed: https://skia.googlesource.com/skia/+/85047175508a24f43eef49359bed215a2a3bb104
>
> R=robertphillips@google.com
>
> Committed: https://skia.googlesource.com/skia/+/71d0c33068d41878cc3117f3761f49300f6b3d54
>
> Committed: https://skia.googlesource.com/skia/+/bd783cd5b62118277b75933c3cd7b9097129259a
>
> Committed: https://skia.googlesource.com/skia/+/198a350051824229aa89a5d6348f5a7fc875c9ca

TBR=robertphillips@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4258

Review URL: https://codereview.chromium.org/1374933004

src/gpu/GrResourceCache.h

@@ -58,8 +58,9 @@ public:
     static const size_t kDefaultMaxSize             = 96 * (1 << 20);
     // Default number of flushes a budgeted resources can go unused in the cache before it is
     // purged. Large values disable the feature (as the ring buffer of flush timestamps would be
-    // large).
-    static const int    kDefaultMaxUnusedFlushes    = 64;
+    // large). This is currently the default until we decide to enable this feature
+    // of the cache by default.
+    static const int    kDefaultMaxUnusedFlushes    = 1024;
 
     /** Used to access functionality needed by GrGpuResource for lifetime management. */
     class ResourceAccess;