cc: Resource list for headup display

cc/layers/heads_up_display_layer_impl.cc

Index: cc/layers/heads_up_display_layer_impl.cc
diff --git a/cc/layers/heads_up_display_layer_impl.cc b/cc/layers/heads_up_display_layer_impl.cc
index fcb2733aee90279959fff97e43148cba86413eb4..772e99ca2c4f647e01c8f51a26455421d5daffd6 100644
--- a/cc/layers/heads_up_display_layer_impl.cc
+++ b/cc/layers/heads_up_display_layer_impl.cc
@@ -81,26 +81,46 @@ scoped_ptr<LayerImpl> HeadsUpDisplayLayerImpl::CreateLayerImpl(
   return HeadsUpDisplayLayerImpl::Create(tree_impl, id()).PassAs<LayerImpl>();
 }
 
+void HeadsUpDisplayLayerImpl::AcquireResource(
+    ResourceProvider* resource_provider) {
+  for (ScopedPtrVector<ScopedResource>::iterator it = resources_.begin();
+       it != resources_.end();
+       ++it) {
+    if (!resource_provider->InUseByConsumer((*it)->id())) {
+      resources_.swap(it, resources_.end() - 1);
+      return;
+    }
+  }
+
+  scoped_ptr<ScopedResource> resource =
+      ScopedResource::Create(resource_provider);
+  resource->Allocate(
+      content_bounds(), ResourceProvider::TextureHintImmutable, RGBA_8888);
+  resources_.push_back(resource.Pass());
+}
+
+void HeadsUpDisplayLayerImpl::ReleaseUnmatchedSizeResources(
+    ResourceProvider* resource_provider) {
+  ScopedPtrVector<ScopedResource> to_be_kept;
+  for (ScopedPtrVector<ScopedResource>::iterator it = resources_.begin();
+       it != resources_.end();
+       ++it) {
+    if ((*it)->size() == content_bounds())
+      to_be_kept.push_back(resources_.take(it));

[danakj, 2014/08/27 13:25:01]

i feel like the common case will be that we keep all the resources, which is
also the worst case for this code.

how about instead doing something like this, where in the common case where we
delete nothing, we just iterate and done.

size_t all_count = resources_.size();
size_t deleted_count = 0;
for (size_t i = 0; i < all_count - deleted_count; ++i) {
  if (...want to delete...) {
    resources_.swap(i, end() - deleted_count - 1);
    ++deleted_count;
  }
}
resources_.erase(end() - deleted_count, end());

[JungJik, 2014/08/28 15:55:38]

thanks for the kind explanation.
however for two reasons, I could not apply your explanation.
one is that erase of ScopedPtrVector supports only iterator type params.
the other is that if in the case that begin() and end() - 1 are same and has
different size with others, we could not remove them.
so I made new patch with stl::partition + fix all nits.
please take a look again. thank you in advance.

+  }
+  resources_.clear();
+
+  resources_.insert_and_take(resources_.begin(), to_be_kept);
+}
+
 bool HeadsUpDisplayLayerImpl::WillDraw(DrawMode draw_mode,
                                        ResourceProvider* resource_provider) {
   if (draw_mode == DRAW_MODE_RESOURCELESS_SOFTWARE)
     return false;
 
-  if (!hud_resource_)
-    hud_resource_ = ScopedResource::Create(resource_provider);
+  ReleaseUnmatchedSizeResources(resource_provider);
 

[danakj, 2014/08/27 13:25:01]

nit: drop whitespace

-  // TODO(danakj): The HUD could swap between two textures instead of creating a
-  // texture every frame in ubercompositor.
-  if (hud_resource_->size() != content_bounds() ||
-      (hud_resource_->id() &&
-       resource_provider->InUseByConsumer(hud_resource_->id()))) {
-    hud_resource_->Free();
-  }
-
-  if (!hud_resource_->id()) {
-    hud_resource_->Allocate(
-        content_bounds(), ResourceProvider::TextureHintImmutable, RGBA_8888);
-  }
+  AcquireResource(resource_provider);
 

[danakj, 2014/08/27 13:25:01]

nit: drop whitespace

   return LayerImpl::WillDraw(draw_mode, resource_provider);
 }
@@ -109,7 +129,7 @@ void HeadsUpDisplayLayerImpl::AppendQuads(
     RenderPass* render_pass,
     const OcclusionTracker<LayerImpl>& occlusion_tracker,
     AppendQuadsData* append_quads_data) {
-  if (!hud_resource_->id())
+  if (!resources_.back()->id())
     return;
 
   SharedQuadState* shared_quad_state =
@@ -130,7 +150,7 @@ void HeadsUpDisplayLayerImpl::AppendQuads(
                quad_rect,
                opaque_rect,
                visible_quad_rect,
-               hud_resource_->id(),
+               resources_.back()->id(),
                premultiplied_alpha,
                uv_top_left,
                uv_bottom_right,
@@ -142,7 +162,7 @@ void HeadsUpDisplayLayerImpl::AppendQuads(
 void HeadsUpDisplayLayerImpl::UpdateHudTexture(
     DrawMode draw_mode,
     ResourceProvider* resource_provider) {
-  if (draw_mode == DRAW_MODE_RESOURCELESS_SOFTWARE || !hud_resource_->id())
+  if (draw_mode == DRAW_MODE_RESOURCELESS_SOFTWARE || !resources_.back()->id())
     return;
 
   SkISize canvas_size;
@@ -179,14 +199,16 @@ void HeadsUpDisplayLayerImpl::UpdateHudTexture(
   DCHECK(pixels);
   gfx::Rect content_rect(content_bounds());
   DCHECK(info.colorType() == kN32_SkColorType);
-  resource_provider->SetPixels(hud_resource_->id(),
+  resource_provider->SetPixels(resources_.back()->id(),
                                static_cast<const uint8_t*>(pixels),
                                content_rect,
                                content_rect,
                                gfx::Vector2d());
 }
 
-void HeadsUpDisplayLayerImpl::ReleaseResources() { hud_resource_.reset(); }
+void HeadsUpDisplayLayerImpl::ReleaseResources() {
+  resources_.clear();
+}
 
 void HeadsUpDisplayLayerImpl::UpdateHudContents() {
   const LayerTreeDebugState& debug_state = layer_tree_impl()->debug_state();