Driver bug workaround: max_msaa_sample_count_4

Bug: chromium: 829614
Change-Id: I54054191815ace6159585dab7dd811ebdc863095
Reviewed-on: https://skia-review.googlesource.com/126983
Commit-Queue: Adrienne Walker <enne@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 727db6c..dc4fc31 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -2786,7 +2786,11 @@
 
     for (int i = 0; i < count; ++i) {
         if (fConfigTable[config].fColorSampleCounts[i] >= requestedCount) {
-            return fConfigTable[config].fColorSampleCounts[i];
+            int count = fConfigTable[config].fColorSampleCounts[i];
+            if (fDriverBugWorkarounds.max_msaa_sample_count_4) {
+                count = SkTMin(count, 4);
+            }
+            return count;
         }
     }
     return 0;