Introduce gpu_fuzzer to fuzz the GPU command buffers

gpu/command_buffer/service/common_decoder.h

Index: gpu/command_buffer/service/common_decoder.h
diff --git a/gpu/command_buffer/service/common_decoder.h b/gpu/command_buffer/service/common_decoder.h
index aca9296cbd60a534aa1f0385c4c94d8ef05683c8..e280cea2dad2ab6d475d2727c44ce3f67d33968b 100644
--- a/gpu/command_buffer/service/common_decoder.h
+++ b/gpu/command_buffer/service/common_decoder.h
@@ -120,6 +120,11 @@ class GPU_EXPORT CommonDecoder : NON_EXPORTED_BASE(public AsyncAPIInterface) {
   }
   CommandBufferEngine* engine() const { return engine_; }
 
+  // Sets the maximum size for buckets.
+  void set_max_bucket_size(size_t max_bucket_size) {
+    max_bucket_size_ = max_bucket_size;
+  }
+
   // Creates a bucket. If the bucket already exists returns that bucket.
   Bucket* CreateBucket(uint32_t bucket_id);
 
@@ -191,6 +196,7 @@ class GPU_EXPORT CommonDecoder : NON_EXPORTED_BASE(public AsyncAPIInterface) {
   #undef COMMON_COMMAND_BUFFER_CMD_OP
 
   CommandBufferEngine* engine_;
+  size_t max_bucket_size_;
 
   typedef std::map<uint32_t, linked_ptr<Bucket>> BucketMap;
   BucketMap buckets_;