Eliminate temporary std::vector in GetNumericHelper and DoGetFramebufferAttachmentParameter

GetNumericHelper and DoGetFramebufferAttachmentParameter were
previously allocating a std::vector of bufsize size and using it
as scratch space before copying the result to the output parameter.

With this change, GetNumericHelper and DoGetFramebufferAttachmentParameter
are modified to write directly into the output parameter.

Bug: 1057747
Change-Id: If19d353a9f7d0bc9aa513deede15afad5c05b67f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2084111Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Rafael Cintron <rafael.cintron@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#746805}

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.h

@@ -384,22 +384,15 @@ class GPU_GLES2_EXPORT GLES2DecoderPassthroughImpl : public GLES2Decoder {
                                 GLsizei* length,
                                 T* params,
                                 GLGetFunction get_call) {
-    // Create a scratch buffer to hold the result of the query
-    std::vector<T> scratch_params(bufsize);
-    get_call(pname, bufsize, length, scratch_params.data());
+    get_call(pname, bufsize, length, params);
 
     // Update the results of the query, if needed
-    error::Error error =
-        PatchGetNumericResults(pname, *length, scratch_params.data());
+    const error::Error error = PatchGetNumericResults(pname, *length, params);
     if (error != error::kNoError) {
       *length = 0;
       return error;
     }
 
-    // Copy into the destination
-    DCHECK(*length <= bufsize);
-    std::copy(scratch_params.data(), scratch_params.data() + *length, params);
-
     return error::kNoError;
   }
 

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

@@ -1680,11 +1680,8 @@ error::Error GLES2DecoderPassthroughImpl::DoGetFramebufferAttachmentParameteriv(
 
   CheckErrorCallbackState();
 
-  // Create a scratch buffer to hold the result of the query
-  std::vector<GLint> scratch_params(bufsize);
   api()->glGetFramebufferAttachmentParameterivRobustANGLEFn(
-      target, updated_attachment, pname, bufsize, length,
-      scratch_params.data());
+      target, updated_attachment, pname, bufsize, length, params);
 
   if (CheckErrorCallbackState()) {
     DCHECK(*length == 0);
@@ -1692,17 +1689,13 @@ error::Error GLES2DecoderPassthroughImpl::DoGetFramebufferAttachmentParameteriv(
   }
 
   // Update the results of the query, if needed
-  error::Error error = PatchGetFramebufferAttachmentParameter(
-      target, updated_attachment, pname, *length, scratch_params.data());
+  const error::Error error = PatchGetFramebufferAttachmentParameter(
+      target, updated_attachment, pname, *length, params);
   if (error != error::kNoError) {
     *length = 0;
     return error;
   }
 
-  // Copy into the destination
-  DCHECK(*length < bufsize);
-  std::copy(scratch_params.data(), scratch_params.data() + *length, params);
-
   return error::kNoError;
 }