Don't create manager objects in ContextGroup when using the passthrough decoder

These objects are not used when the passthrough command decoder is in
use.  This saves several GPU memory allocations in TextureManager for
default and black textures.

Saves ~2 MB per context.

BUG=1046613
BUG=1030835

Change-Id: I66c6acf28580742bc313d8cf79de80f7f7d98305
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2028291
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736631}

gpu/command_buffer/service/context_group.cc

@@ -263,13 +263,17 @@ gpu::ContextResult ContextGroup::Initialize(
                 &uniform_buffer_offset_alignment_);
   }
 
-  buffer_manager_ = std::make_unique<BufferManager>(memory_tracker_.get(),
-                                                    feature_info_.get());
-  renderbuffer_manager_ = std::make_unique<RenderbufferManager>(
-      memory_tracker_.get(), max_renderbuffer_size, max_samples,
-      feature_info_.get());
-  shader_manager_ = std::make_unique<ShaderManager>(progress_reporter_);
-  sampler_manager_ = std::make_unique<SamplerManager>(feature_info_.get());
+  // Managers are not used by the passthrough command decoder. Save memory by
+  // not allocating them.
+  if (!use_passthrough_cmd_decoder_) {
+    buffer_manager_ = std::make_unique<BufferManager>(memory_tracker_.get(),
+                                                      feature_info_.get());
+    renderbuffer_manager_ = std::make_unique<RenderbufferManager>(
+        memory_tracker_.get(), max_renderbuffer_size, max_samples,
+        feature_info_.get());
+    shader_manager_ = std::make_unique<ShaderManager>(progress_reporter_);
+    sampler_manager_ = std::make_unique<SamplerManager>(feature_info_.get());
+  }
 
   // Lookup GL things we need to know.
   const GLint kGLES2RequiredMinimumVertexAttribs = 8u;
@@ -389,11 +393,15 @@ gpu::ContextResult ContextGroup::Initialize(
                  feature_info_->workarounds().max_3d_array_texture_size);
   }
 
-  texture_manager_.reset(new TextureManager(
-      memory_tracker_.get(), feature_info_.get(), max_texture_size,
-      max_cube_map_texture_size, max_rectangle_texture_size,
-      max_3d_texture_size, max_array_texture_layers, bind_generates_resource_,
-      progress_reporter_, discardable_manager_));
+  // Managers are not used by the passthrough command decoder. Save memory by
+  // not allocating them.
+  if (!use_passthrough_cmd_decoder_) {
+    texture_manager_.reset(new TextureManager(
+        memory_tracker_.get(), feature_info_.get(), max_texture_size,
+        max_cube_map_texture_size, max_rectangle_texture_size,
+        max_3d_texture_size, max_array_texture_layers, bind_generates_resource_,
+        progress_reporter_, discardable_manager_));
+  }
 
   const GLint kMinTextureImageUnits = 8;
   const GLint kMinVertexTextureImageUnits = 0;
@@ -523,14 +531,18 @@ gpu::ContextResult ContextGroup::Initialize(
     }
   }
 
-  path_manager_ = std::make_unique<PathManager>();
+  // Managers are not used by the passthrough command decoder. Save memory by
+  // not allocating them.
+  if (!use_passthrough_cmd_decoder_) {
+    path_manager_ = std::make_unique<PathManager>();
 
-  program_manager_ = std::make_unique<ProgramManager>(
-      program_cache_, max_varying_vectors_, max_draw_buffers_,
-      max_dual_source_draw_buffers_, max_vertex_attribs_, gpu_preferences_,
-      feature_info_.get(), progress_reporter_);
+    program_manager_ = std::make_unique<ProgramManager>(
+        program_cache_, max_varying_vectors_, max_draw_buffers_,
+        max_dual_source_draw_buffers_, max_vertex_attribs_, gpu_preferences_,
+        feature_info_.get(), progress_reporter_);
 
-  texture_manager_->Initialize();
+    texture_manager_->Initialize();
+  }
 
   decoders_.push_back(decoder->AsWeakPtr());
   return gpu::ContextResult::kSuccess;

media/gpu/command_buffer_helper.cc

@@ -15,7 +15,6 @@
 #include "gpu/command_buffer/service/decoder_context.h"
 #include "gpu/command_buffer/service/scheduler.h"
 #include "gpu/command_buffer/service/sync_point_manager.h"
-#include "gpu/command_buffer/service/texture_manager.h"
 #include "gpu/ipc/service/command_buffer_stub.h"
 #include "gpu/ipc/service/gpu_channel.h"
 #include "media/gpu/gles2_decoder_helper.h"

media/gpu/gles2_decoder_helper.cc

@@ -14,7 +14,6 @@
 #include "gpu/command_buffer/service/context_group.h"
 #include "gpu/command_buffer/service/decoder_context.h"
 #include "gpu/command_buffer/service/mailbox_manager.h"
-#include "gpu/command_buffer/service/texture_manager.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/scoped_binders.h"
 
@@ -28,10 +27,7 @@ class GLES2DecoderHelperImpl : public GLES2DecoderHelper {
       : decoder_(decoder) {
     DCHECK(decoder_);
     gpu::gles2::ContextGroup* group = decoder_->GetContextGroup();
-    texture_manager_ = group->texture_manager();
     mailbox_manager_ = group->mailbox_manager();
-    // TODO(sandersd): Support GLES2DecoderPassthroughImpl.
-    DCHECK(texture_manager_);
     DCHECK(mailbox_manager_);
   }
 
@@ -97,7 +93,6 @@ class GLES2DecoderHelperImpl : public GLES2DecoderHelper {
 
  private:
   gpu::DecoderContext* decoder_;
-  gpu::gles2::TextureManager* texture_manager_;
   gpu::MailboxManager* mailbox_manager_;
   THREAD_CHECKER(thread_checker_);