Optimize GetBucketContents

gpu/command_buffer/service/common_decoder.cc

Index: gpu/command_buffer/service/common_decoder.cc
diff --git a/gpu/command_buffer/service/common_decoder.cc b/gpu/command_buffer/service/common_decoder.cc
index 7b28603edcdd8ab1e01a85a5746eab0b688d3c7a..c47ac61ce1388ba8f1defbf7b1c0739d6a8f9611 100644
--- a/gpu/command_buffer/service/common_decoder.cc
+++ b/gpu/command_buffer/service/common_decoder.cc
@@ -286,24 +286,40 @@ error::Error CommonDecoder::HandleSetBucketDataImmediate(
   return error::kNoError;
 }
 
-error::Error CommonDecoder::HandleGetBucketSize(
+error::Error CommonDecoder::HandleGetBucketStart(
     uint32 immediate_data_size,
-    const cmd::GetBucketSize& args) {
+    const cmd::GetBucketStart& args) {
   uint32 bucket_id = args.bucket_id;
-  uint32* data = GetSharedMemoryAs<uint32*>(
-      args.shared_memory_id, args.shared_memory_offset, sizeof(*data));
-  if (!data) {
+  uint32* result = GetSharedMemoryAs<uint32*>(
+      args.result_memory_id, args.result_memory_offset, sizeof(*result));
+  int32 data_memory_id = args.data_memory_id;
+  uint32 data_memory_offset = args.data_memory_offset;
+  uint32 data_memory_size = args.data_memory_size;
+  uint8* data = NULL;
+  if (data_memory_size != 0 || data_memory_id != 0 || data_memory_offset != 0) {
+    data = GetSharedMemoryAs<uint8*>(
+        args.data_memory_id, args.data_memory_offset, args.data_memory_size);
+    if (!data) {
+      return error::kInvalidArguments;
+    }
+  }
+  if (!result) {
     return error::kInvalidArguments;
   }
   // Check that the client initialized the result.
-  if (*data != 0) {
+  if (*result != 0) {
     return error::kInvalidArguments;
   }
   Bucket* bucket = GetBucket(bucket_id);
   if (!bucket) {
     return error::kInvalidArguments;
   }
-  *data = bucket->size();
+  uint32 bucket_size = bucket->size();
+  *result = bucket_size;
+  if (data) {
+    uint32 size = std::min(data_memory_size, bucket_size);
+    memcpy(data, bucket->GetData(0, size), size);
+  }
   return error::kNoError;
 }