Stabilize empty rect handling in EnclosingRect.

ui/gfx/geometry/size_f.h

Index: ui/gfx/geometry/size_f.h
diff --git a/ui/gfx/geometry/size_f.h b/ui/gfx/geometry/size_f.h
index 9d1bb5d7e3ed6c18d4ff3d3193a510ae85c70c48..2283163c8ae91a7fcfb32a500545dc923b256535 100644
--- a/ui/gfx/geometry/size_f.h
+++ b/ui/gfx/geometry/size_f.h
@@ -19,7 +19,7 @@ class GFX_EXPORT SizeF {
  public:
   constexpr SizeF() : width_(0.f), height_(0.f) {}
   constexpr SizeF(float width, float height)
-      : width_(width >= 0 ? width : 0), height_(height >= 0 ? height : 0) {}
+      : width_(clamp(width)), height_(clamp(height)) {}
 
   constexpr explicit SizeF(const Size& size)
       : SizeF(static_cast<float>(size.width()),
@@ -28,8 +28,8 @@ class GFX_EXPORT SizeF {
   constexpr float width() const { return width_; }
   constexpr float height() const { return height_; }
 
-  void set_width(float width) { width_ = fmaxf(0, width); }
-  void set_height(float height) { height_ = fmaxf(0, height); }
+  void set_width(float width) { width_ = clamp(width); }
+  void set_height(float height) { height_ = clamp(height); }
 
   float GetArea() const;
 
@@ -43,7 +43,7 @@ class GFX_EXPORT SizeF {
   void SetToMin(const SizeF& other);
   void SetToMax(const SizeF& other);
 
-  bool IsEmpty() const { return !width() || !height(); }
+  bool IsEmpty() const { return !height_ || !width_; }
 
   void Scale(float scale) {
     Scale(scale, scale);
@@ -58,6 +58,9 @@ class GFX_EXPORT SizeF {
  private:
   float width_;
   float height_;
+  static constexpr float kTrivial = 8.f * std::numeric_limits<float>::epsilon();
+  static constexpr float clamp(float f) { return f > kTrivial ? f : 0.f; }
+  friend float SizeFPrivateMatch();  // Test access to the kTrivial constant.

[danakj, 2017/03/28 18:00:20]

make friends the first thing in the private block and whitespace below. you can
use FRIEND_TEST to friend access to the constant
https://cs.chromium.org/chromium/src/testing/gtest/include/gtest/gtest_prod.h...

[Peter Mayo, 2017/03/28 20:11:21]

Done.

 };
 
 inline bool operator==(const SizeF& lhs, const SizeF& rhs) {