Add tinted static UI resource cache

ui/android/resources/resource_manager_impl.cc

Index: ui/android/resources/resource_manager_impl.cc
diff --git a/ui/android/resources/resource_manager_impl.cc b/ui/android/resources/resource_manager_impl.cc
index 61c7bdad554d3f7999494da3fad752f8e48e2726..d8aec1dfa10ba908446cd00803713b490265bd8f 100644
--- a/ui/android/resources/resource_manager_impl.cc
+++ b/ui/android/resources/resource_manager_impl.cc
@@ -14,6 +14,9 @@
 #include "base/trace_event/trace_event.h"
 #include "cc/resources/scoped_ui_resource.h"
 #include "jni/ResourceManager_jni.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkColorFilter.h"
 #include "ui/android/resources/ui_resource_provider.h"
 #include "ui/android/window_android.h"
 #include "ui/gfx/android/java_bitmap.h"
@@ -73,6 +76,83 @@ ResourceManager::Resource* ResourceManagerImpl::GetResource(
   return resource;
 }
 
+void ResourceManagerImpl::RemoveUnusedTints(
+    const std::unordered_set<int>& used_tints) {
+  // Iterate over the currently cached tints and remove ones that were not
+  // used as defined in |used_tints|.
+  for (const auto& a : tinted_resources_) {
+    if (used_tints.find(a.first) == used_tints.end()) {
+        tinted_resources_.erase(a.first);

[aelias_OOO_until_Jul13, 2016/09/07 19:34:44]

I think the for loop implicit iterator would still be pointing at erased item so
I'm not certain it's correct?  The usual pattern for this is to use the return
value of erase() to advance, see the similar thing in
TabListSceneLayer::FinishBuildingFrame.

[mdjones, 2016/09/08 16:34:44]

Done.

+    }
+  }
+}
+
+ResourceManager::Resource* ResourceManagerImpl::GetStaticResourceWithTint(
+    int res_id,
+    int tint_color) {
+  auto item = tinted_resources_.find(tint_color);

[aelias_OOO_until_Jul13, 2016/09/07 19:34:44]

I think the iterator name wouldn't be ridiculously long in this case so I'd
prefer avoiding "auto" for clarity.

[mdjones, 2016/09/08 16:34:44]

Done.

+  ResourceMap* resource_map;
+  if (item == tinted_resources_.end()) {
+    resource_map = new ResourceMap();
+    tinted_resources_.insert({tint_color, resource_map});
+  } else {
+    resource_map = item->second;
+  }
+
+  Resource* tinted_resource = resource_map->Lookup(res_id);
+
+  // If the resource is already cached, use it.
+  if (tinted_resource)
+    return tinted_resource;
+
+  ResourceManager::Resource* base_image =
+      GetResource(ANDROID_RESOURCE_TYPE_STATIC, res_id);
+  if (!base_image)

[aelias_OOO_until_Jul13, 2016/09/07 19:34:44]

What is this scenario, exactly?  Can we DCHECK?

[mdjones, 2016/09/08 16:34:44]

Resource might not be ready. DCHECK should be fine.

+    return nullptr;
+
+  SkBitmap tinted_bitmap;

[aelias_OOO_until_Jul13, 2016/09/07 19:34:44]

Could you add a TRACE_EVENT0(browser,
"ResourceManagerImpl::GetStaticResourceWithTint") above this line?  The tint
texture creation has a risk of introducing small janks, this will make it more
easily visible in traces.

[mdjones, 2016/09/08 16:34:44]

Done.

+  tinted_bitmap.allocPixels(SkImageInfo::MakeN32Premul(base_image->size.width(),
+      base_image->size.height()));
+
+  SkCanvas canvas(tinted_bitmap);
+  canvas.clear(SK_ColorTRANSPARENT);
+
+  // Build a color filter to use on the base resource. This filter multiplies
+  // the RGB components by the components of the new color but retains the
+  // alpha of the original image.
+  SkPaint color_filter;
+  SkScalar color_matrix[] = {
+      SkColorGetR(tint_color) / 255.0f, 0, 0, 0, 0,
+      0, SkColorGetG(tint_color) / 255.0f, 0, 0, 0,
+      0, 0, SkColorGetB(tint_color) / 255.0f, 0, 0,
+      0, 0, 0, 1.0f, 0
+  };
+  color_filter.setColorFilter(
+      SkColorFilter::MakeMatrixFilterRowMajor255(color_matrix));

[aelias_OOO_until_Jul13, 2016/09/07 19:34:44]

Could you switch to SkFilter::MakeModeFilter(color, SkXfermode::kModulate_Mode)
like I suggested earlier?  It should be faster.

[mdjones, 2016/09/08 16:34:44]

Done.

+
+  // Draw the resource and make it immutable.
+  base_image->ui_resource->GetBitmap(base_image->ui_resource->id(), false)
+      .DrawToCanvas(&canvas, &color_filter);
+  tinted_bitmap.setImmutable();
+
+  // Create a UI resource from the new bitmap.
+  tinted_resource = new Resource();
+  tinted_resource->size = gfx::Size(base_image->size);
+  tinted_resource->padding = gfx::Rect(base_image->padding);
+  tinted_resource->aperture = gfx::Rect(base_image->aperture);
+  tinted_resource->ui_resource = cc::ScopedUIResource::Create(host_,
+      cc::UIResourceBitmap(tinted_bitmap));
+
+  resource_map->AddWithID(tinted_resource, res_id);
+
+  return tinted_resource;
+}
+
+void ResourceManagerImpl::ClearTintedResourceCache(JNIEnv* env,
+    const JavaRef<jobject>& jobj) {
+  tinted_resources_.clear();
+}
+
 void ResourceManagerImpl::PreloadResource(AndroidResourceType res_type,
                                           int res_id) {
   DCHECK_GE(res_type, ANDROID_RESOURCE_TYPE_FIRST);