A host of micro-optimizations and a refactor of TimeForBoundsToIntersect

cc/tile_priority.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TILE_PRIORITY_H_
 #define CC_TILE_PRIORITY_H_
 
 #include <limits>
 
 #include "base/memory/ref_counted.h"
@@ skipping 43 matching lines @@
     distance_to_visible_in_pixels =
       std::min(active.distance_to_visible_in_pixels,
                pending.distance_to_visible_in_pixels);
   }
 
   float time_to_needed_in_seconds() const {
     return std::min(time_to_visible_in_seconds,
                     time_to_ideal_resolution_in_seconds);
   }
 
-  static const double kMaxTimeToVisibleInSeconds;
+  static const float kMaxTimeToVisibleInSeconds;
 
-  static int manhattanDistance(const gfx::RectF& a, const gfx::RectF& b);
+  static inline float manhattanDistance(const gfx::RectF& a, const gfx::RectF& b) {
+    // Compute the union explicitly.
+    gfx::RectF c = gfx::RectF(
+        std::min(a.x(), b.x()),
+        std::min(a.y(), b.y()),
+        std::max(a.right(), b.right() - std::min(a.x(), b.x())),
+        std::max(a.bottom(), b.bottom() - std::min(a.y(), b.y())));
+
+    // Rects touching the edge of the screen should not be considered visible.
+    // So we add 1 pixel here to avoid that situation.
+    float x = std::max(0.0f, c.width() - a.width() - b.width() + 1.0f);
+    float y = std::max(0.0f, c.height() - a.height() - b.height() + 1.0f);
+    return (x + y);
+  }
 
   // Calculate the time for the |current_bounds| to intersect with the
   // |target_bounds| given its previous location and time delta.
   // This function should work for both scaling and scrolling case.
-  static double TimeForBoundsToIntersect(gfx::RectF previous_bounds,
-                                         gfx::RectF current_bounds,
-                                         double time_delta,
-                                         gfx::RectF target_bounds);
+  static float TimeForBoundsToIntersect(const gfx::RectF& previous_bounds,
+                                        const gfx::RectF& current_bounds,
+                                        float time_delta,
+                                        const gfx::RectF& target_bounds);
 
   TileResolution resolution;
   float time_to_visible_in_seconds;
   float time_to_ideal_resolution_in_seconds;
   float distance_to_visible_in_pixels;
 };
 
 enum TileMemoryLimitPolicy {
   // Nothing.
   ALLOW_NOTHING,
@@ skipping 25 matching lines @@
   TileMemoryLimitPolicy memory_limit_policy;
 
   size_t memory_limit_in_bytes;
 
   TreePriority tree_priority;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILE_PRIORITY_H_