Make tile size a function of the device scale factor.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 0c49515356840a94b8656cfa4e86cbe285a58965..be4cd238f58037f899670ba784b88c86b2039524 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -38,6 +38,7 @@
 #include "cc/proto/compositor_message.pb.h"
 #include "cc/resources/single_release_callback.h"
 #include "cc/scheduler/begin_frame_source.h"
+#include "cc/tiles/picture_layer_tiling.h"
 #include "cc/trees/latency_info_swap_promise_monitor.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/remote_proto_channel.h"
@@ -62,7 +63,6 @@
 
 #if defined(OS_ANDROID)
 #include "base/android/build_info.h"
-#include "ui/gfx/android/device_display_info.h"
 #endif
 
 namespace base {
@@ -136,58 +136,6 @@ cc::LayerSelection ConvertWebSelection(const WebSelection& web_selection) {
   return cc_selection;
 }
 
-gfx::Size CalculateDefaultTileSize(float initial_device_scale_factor) {
-  int default_tile_size = 256;
-#if defined(OS_ANDROID)
-  // TODO(epenner): unify this for all platforms if it
-  // makes sense (http://crbug.com/159524)
-
-  gfx::DeviceDisplayInfo info;
-  bool real_size_supported = true;
-  int display_width = info.GetPhysicalDisplayWidth();
-  int display_height = info.GetPhysicalDisplayHeight();
-  if (display_width == 0 || display_height == 0) {
-    real_size_supported = false;
-    display_width = info.GetDisplayWidth();
-    display_height = info.GetDisplayHeight();
-  }
-
-  int portrait_width = std::min(display_width, display_height);
-  int landscape_width = std::max(display_width, display_height);
-
-  if (real_size_supported) {
-    // Maximum HD dimensions should be 768x1280
-    // Maximum FHD dimensions should be 1200x1920
-    if (portrait_width > 768 || landscape_width > 1280)
-      default_tile_size = 384;
-    if (portrait_width > 1200 || landscape_width > 1920)
-      default_tile_size = 512;
-
-    // Adjust for some resolutions that barely straddle an extra
-    // tile when in portrait mode. This helps worst case scroll/raster
-    // by not needing a full extra tile for each row.
-    if (default_tile_size == 256 && portrait_width == 768)
-      default_tile_size += 32;
-    if (default_tile_size == 384 && portrait_width == 1200)
-      default_tile_size += 32;
-  } else {
-    // We don't know the exact resolution due to screen controls etc.
-    // So this just estimates the values above using tile counts.
-    int numTiles = (display_width * display_height) / (256 * 256);
-    if (numTiles > 16)
-      default_tile_size = 384;
-    if (numTiles >= 40)
-      default_tile_size = 512;
-  }
-#elif defined(OS_CHROMEOS) || defined(OS_MACOSX)
-  // Use 512 for high DPI (dsf=2.0f) devices.
-  if (initial_device_scale_factor >= 2.0f)
-    default_tile_size = 512;
-#endif
-
-  return gfx::Size(default_tile_size, default_tile_size);
-}
-
 // Check cc::TopControlsState, and blink::WebTopControlsState
 // are kept in sync.
 static_assert(int(blink::WebTopControlsBoth) == int(cc::BOTH),
@@ -289,38 +237,6 @@ cc::LayerTreeSettings RenderWidgetCompositor::GenerateLayerTreeSettings(
   settings.main_frame_before_activation_enabled =
       cmd.HasSwitch(cc::switches::kEnableMainFrameBeforeActivation);
 
-  // TODO(danakj): This should not be a setting O_O; it should change when the
-  // device scale factor on LayerTreeHost changes.
-  settings.default_tile_size = CalculateDefaultTileSize(device_scale_factor);
-  if (cmd.HasSwitch(switches::kDefaultTileWidth)) {
-    int tile_width = 0;
-    GetSwitchValueAsInt(cmd, switches::kDefaultTileWidth, 1,
-                        std::numeric_limits<int>::max(), &tile_width);
-    settings.default_tile_size.set_width(tile_width);
-  }
-  if (cmd.HasSwitch(switches::kDefaultTileHeight)) {
-    int tile_height = 0;
-    GetSwitchValueAsInt(cmd, switches::kDefaultTileHeight, 1,
-                        std::numeric_limits<int>::max(), &tile_height);
-    settings.default_tile_size.set_height(tile_height);
-  }
-
-  int max_untiled_layer_width = settings.max_untiled_layer_size.width();
-  if (cmd.HasSwitch(switches::kMaxUntiledLayerWidth)) {
-    GetSwitchValueAsInt(cmd, switches::kMaxUntiledLayerWidth, 1,
-                        std::numeric_limits<int>::max(),
-                        &max_untiled_layer_width);
-  }
-  int max_untiled_layer_height = settings.max_untiled_layer_size.height();
-  if (cmd.HasSwitch(switches::kMaxUntiledLayerHeight)) {
-    GetSwitchValueAsInt(cmd, switches::kMaxUntiledLayerHeight, 1,
-                        std::numeric_limits<int>::max(),
-                        &max_untiled_layer_height);
-  }
-
-  settings.max_untiled_layer_size = gfx::Size(max_untiled_layer_width,
-                                           max_untiled_layer_height);
-
   settings.gpu_rasterization_msaa_sample_count =
       compositor_deps->GetGpuRasterizationMSAASampleCount();
   settings.gpu_rasterization_forced =
@@ -405,6 +321,9 @@ cc::LayerTreeSettings RenderWidgetCompositor::GenerateLayerTreeSettings(
   bool using_synchronous_compositor =
       GetContentClient()->UsingSynchronousCompositing();
 
+  // TODO(crbug.com/622885): Android viewport is assumed to be fixed forever.
+  settings.use_viewport_for_tile_size = true;
+
   // We can't use GPU rasterization on low-end devices, because the Ganesh
   // cache would consume too much memory.
   if (base::SysInfo::IsLowEndDevice())