Reduce unique_ptr scope to save memory

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index c480b71567dca3814c19aeca0b4f7185bc338e42..1a998c796c0233fa70d81126153aaeb224f44718 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2637,17 +2637,22 @@ bool BackTexture::AllocateStorage(
     DestroyNativeGpuMemoryBuffer(true);
     success = AllocateNativeGpuMemoryBuffer(size, format, zero);
   } else {
-    std::unique_ptr<char[]> zero_data;
-    if (zero) {
-      zero_data.reset(new char[image_size]);
-      memset(zero_data.get(), 0, image_size);
+    {
+      // Add extra scope to destroy zero_data and the object it owns right
+      // after its usage.
+      std::unique_ptr<char[]> zero_data;
+      if (zero) {
+        zero_data.reset(new char[image_size]);
+        memset(zero_data.get(), 0, image_size);
+      }
+
+      glTexImage2D(Target(),
+        0,  // mip level
+        format, size.width(), size.height(),
+        0,  // border
+        format, GL_UNSIGNED_BYTE, zero_data.get());
     }
 
-    glTexImage2D(Target(),
-                 0,  // mip level
-                 format, size.width(), size.height(),
-                 0,  // border
-                 format, GL_UNSIGNED_BYTE, zero_data.get());
     decoder_->texture_manager()->SetLevelInfo(
         texture_ref_.get(), Target(),
         0,  // level
@@ -12258,20 +12263,24 @@ bool GLES2DecoderImpl::ClearLevel(Texture* texture,
     tile_height = height;
   }
 
-  // Assumes the size has already been checked.
-  std::unique_ptr<char[]> zero(new char[size]);
-  memset(zero.get(), 0, size);
-  glBindTexture(texture->target(), texture->service_id());
-
-  GLint y = 0;
-  while (y < height) {
-    GLint h = y + tile_height > height ? height - y : tile_height;
-    glTexSubImage2D(
+  {
+    // Add extra scope to destroy zero and the object it owns right
+    // after its usage.
+    // Assumes the size has already been checked.
+    std::unique_ptr<char[]> zero(new char[size]);
+    memset(zero.get(), 0, size);
+    glBindTexture(texture->target(), texture->service_id());
+
+    GLint y = 0;
+    while (y < height) {
+      GLint h = y + tile_height > height ? height - y : tile_height;
+      glTexSubImage2D(
         target, level, xoffset, yoffset + y, width, h,
         TextureManager::AdjustTexFormat(feature_info_.get(), format),
         type,
         zero.get());
-    y += tile_height;
+      y += tile_height;
+    }
   }
   TextureRef* bound_texture =
       texture_manager()->GetTextureInfoForTarget(&state_, texture->target());
@@ -12304,11 +12313,15 @@ bool GLES2DecoderImpl::ClearCompressedTextureLevel(Texture* texture,
                "bytes_required", bytes_required);
 
   glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
-  std::unique_ptr<char[]> zero(new char[bytes_required]);
-  memset(zero.get(), 0, bytes_required);
-  glBindTexture(texture->target(), texture->service_id());
-  glCompressedTexSubImage2D(
+  {
+    // Add extra scope to destroy zero and the object it owns right
+    // after its usage.
+    std::unique_ptr<char[]> zero(new char[bytes_required]);
+    memset(zero.get(), 0, bytes_required);
+    glBindTexture(texture->target(), texture->service_id());
+    glCompressedTexSubImage2D(
       target, level, 0, 0, width, height, format, bytes_required, zero.get());
+  }
   TextureRef* bound_texture =
       texture_manager()->GetTextureInfoForTarget(&state_, texture->target());
   glBindTexture(texture->target(),
@@ -13870,12 +13883,18 @@ void GLES2DecoderImpl::DoCopyTexImage2D(
 
   if (src.x() != x || src.y() != y ||
       src.width() != width || src.height() != height) {
-    // some part was clipped so clear the rect.
-    std::unique_ptr<char[]> zero(new char[pixels_size]);
-    memset(zero.get(), 0, pixels_size);
-    glTexImage2D(target, level, TextureManager::AdjustTexInternalFormat(
-                                    feature_info_.get(), internal_format),
-                 width, height, border, format, type, zero.get());
+    {
+      // Add extra scope to destroy zero and the object it owns right
+      // after its usage.
+      // some part was clipped so clear the rect.
+
+      std::unique_ptr<char[]> zero(new char[pixels_size]);
+      memset(zero.get(), 0, pixels_size);
+      glTexImage2D(target, level, TextureManager::AdjustTexInternalFormat(
+        feature_info_.get(), internal_format),
+        width, height, border, format, type, zero.get());

[stanisc, 2016/11/09 22:33:03]

You could consider something like replacing zero.get() with
std::vector<char>(pixel_size). That would allocate and zero the buffer in place
and free it right after returning from glTexImage2D call. 
But the end result would be exactly the same and the existing implementation is
probably more straightforward.

[chengx, 2016/11/10 22:43:46]

Thanks for your suggestion. I will the current version for now.

+    }
+
     if (!src.IsEmpty()) {
       GLint destX = src.x() - x;
       GLint destY = src.y() - y;