Stabilize empty rect handling in EnclosingRect.

ui/gfx/geometry/rect_conversions.cc

 // Copyright (c) 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.
 
 #include "ui/gfx/geometry/rect_conversions.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/logging.h"
 #include "ui/gfx/geometry/safe_integer_conversions.h"
 
 namespace gfx {
 
+// This is the minimum size of a float rect dimension for use to include it
+// in the enclosing int rect.
+static const float kEmptyDimension = 0.1f;

[Peter Mayo, 2017/03/20 18:53:50]

That is too big - it causes unittests to fail. (occlusion tests)

.09 is empirically enough to make the tests pass.

Interesting.

 Rect ToEnclosingRect(const RectF& rect) {
   int min_x = ToFlooredInt(rect.x());
   int min_y = ToFlooredInt(rect.y());
   float max_x = rect.right();
   float max_y = rect.bottom();
   int width =
-      rect.width() == 0
+      rect.width() < kEmptyDimension
           ? 0
           : std::max(
                 ToCeiledInt(static_cast<double>(ToCeiledInt(max_x)) - min_x),
                 0);
   int height =
-      rect.height() == 0
+      rect.height() < kEmptyDimension
           ? 0
           : std::max(
                 ToCeiledInt(static_cast<double>(ToCeiledInt(max_y)) - min_y),
                 0);
   return Rect(min_x, min_y, width, height);
 }
 
 Rect ToEnclosedRect(const RectF& rect) {
   int min_x = ToCeiledInt(rect.x());
   int min_y = ToCeiledInt(rect.y());
@@ skipping 47 matching lines @@
 
 Rect ToFlooredRectDeprecated(const RectF& rect) {
   return Rect(ToFlooredInt(rect.x()),
               ToFlooredInt(rect.y()),
               ToFlooredInt(rect.width()),
               ToFlooredInt(rect.height()));
 }
 
 }  // namespace gfx