Fix use_image_texture_target inconsistencies

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index cbd42b63040ff89588a5a9436c2f661e4a8ad45e..cce3c3315f58ea629e93777436402fa6dc61e62a 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -37,7 +37,6 @@
 #include "ui/compositor/dip_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animator_collection.h"
-#include "ui/gl/gl_context.h"
 #include "ui/gl/gl_switches.h"
 
 namespace {
@@ -159,19 +158,19 @@ Compositor::Compositor(ui::ContextFactory* context_factory,
   // doesn't currently support partial raster.
   settings.use_partial_raster = !settings.use_zero_copy;
 
-  // Use CPU_READ_WRITE_PERSISTENT memory buffers to support partial tile
-  // raster if needed.
-  gfx::BufferUsage usage =
-      settings.use_partial_raster
-          ? gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT
-          : gfx::BufferUsage::GPU_READ_CPU_READ_WRITE;
-
-  for (size_t format = 0;
-      format < static_cast<size_t>(gfx::BufferFormat::LAST) + 1; format++) {
-    DCHECK_GT(settings.use_image_texture_targets.size(), format);
-    settings.use_image_texture_targets[format] =
-        context_factory_->GetImageTextureTarget(
-            static_cast<gfx::BufferFormat>(format), usage);
+  // Populate buffer_to_texture_target_map for all buffer usage/formats.
+  for (size_t usage_idx = 0;

[danakj, 2016/07/19 20:37:56]

why size_t and not int?

[ericrk, 2016/07/19 21:47:46]

No reason - previous code used size_t, but I can't see a strong reason why -
changing to int.

+       usage_idx < static_cast<size_t>(gfx::BufferUsage::LAST) + 1;

[danakj, 2016/07/19 20:37:56]

nit: use <= instead of +1

[ericrk, 2016/07/19 21:47:46]

Done.

+       ++usage_idx) {
+    gfx::BufferUsage usage = static_cast<gfx::BufferUsage>(usage_idx);
+    for (size_t format_idx = 0;

[danakj, 2016/07/19 20:37:56]

why size_t and not int?

[ericrk, 2016/07/19 21:47:46]

Done.

+         format_idx < static_cast<size_t>(gfx::BufferFormat::LAST) + 1;

[danakj, 2016/07/19 20:37:56]

nit: <= instead of +1

[ericrk, 2016/07/19 21:47:46]

Done.

+         ++format_idx) {
+      gfx::BufferFormat format = static_cast<gfx::BufferFormat>(format_idx);
+      uint32_t target = context_factory_->GetImageTextureTarget(format, usage);
+      settings.renderer_settings.buffer_to_texture_target_map.emplace(
+          cc::BufferToTextureTargetKey(usage, format), target);
+    }
   }
 
   // Note: Only enable image decode tasks if we have more than one worker