Add a version of gpu_fuzzer that is backed by the NULL ANGLE backend

gpu/BUILD.gn

Index: gpu/BUILD.gn
diff --git a/gpu/BUILD.gn b/gpu/BUILD.gn
index e2cd4830b9c4193deefd588d115199f235af93df..88efa684dcdf9ffc6024f53a5e99b246bf168f67 100644
--- a/gpu/BUILD.gn
+++ b/gpu/BUILD.gn
@@ -404,3 +404,27 @@ fuzzer_test("gpu_fuzzer") {
     "use_traces=1",
   ]
 }
+
+fuzzer_test("gpu_fuzzer_angle") {
+  sources = [
+    "command_buffer/tests/fuzzer_main.cc",
+  ]
+
+  defines = [ "GPU_FUZZER_USE_ANGLE" ]
+
+  deps = [
+    ":gpu",
+    "//base",
+    "//base/third_party/dynamic_annotations",
+    "//gpu/command_buffer/common:gles2_utils",
+    "//ui/gfx/geometry",
+    "//ui/gl",
+    "//ui/gl:test_support",
+  ]
+
+  libfuzzer_options = [
+    "max_len=16384",
+    "use_traces=1",

[mmoroz, 2016/12/01 15:28:31]

That flag seems to be out-of-date (or may be it is ON by default now?):

WARNING: unrecognized flag '-use_traces=1'; use -help=1 to list all flags

[piman, 2016/12/01 18:19:28]

Thanks, I'll take it out (including above)

[piman, 2016/12/08 23:21:46]

Done.

+    "rss_limit_mb=4096",

[mmoroz, 2016/12/01 15:26:05]

How important is this memory volume? Our current VMs have 4 GB of RAM each, so
running fuzzers with rss_limit_mb of 4096 MB doesn't seem to be a good idea at
the moment.

[piman, 2016/12/01 18:19:28]

Right now it needs around 3.5GB just to run the existing corpus. I was planning
on looking at memory usage in details afterwards, but I guess I need to do that
homework first.

[mmoroz, 2016/12/01 18:22:52]

Hm, yeah, we probably need to shrink it if that's possible. Have you tried to
minimize the corpus?

mkdir minimized_corpus_dir && ./fuzzer minimized_corpus_dir initial_corpus_dir
-merge=1

Maybe after that it won't be using so much memory...

[piman, 2016/12/08 23:21:46]

Removed flag, as discussed.

+  ]
+}