Add cap to number of oplists we execute before flushing to the gpu.

This fixes a crash we saw when we switch vulkan copies as draws to creating
their own secondary command buffer. The crash came from the perf blendmode
tests when using an advanced blend mode. They would do 1000 draws which forced
us into creating 2000 command buffers (since the dst copies and the normal draws
each used them). I tested without the copies as draws change and just increasing
the total number of draws we do and was able to repro the crash.

Besides fixing the above OOM crash, I am also seeing a 5-10% perf gain on the
blendmode micro benches which is nice

Bug: skia:
Change-Id: I9266ea0ba02a755f54dabd4ee804963ab0c9b684
Reviewed-on: https://skia-review.googlesource.com/c/175436
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/gn/tests.gni b/gn/tests.gni
index 66fc2b8..351efae 100644
--- a/gn/tests.gni
+++ b/gn/tests.gni
@@ -98,6 +98,7 @@
   "$_tests/GrMemoryPoolTest.cpp",
   "$_tests/GrMeshTest.cpp",
   "$_tests/GrMipMappedTest.cpp",
+  "$_tests/GrOpListFlushTest.cpp",
   "$_tests/GrPipelineDynamicStateTest.cpp",
   "$_tests/GrPorterDuffTest.cpp",
   "$_tests/GrShapeTest.cpp",