Make various gfx classes more amenable to use as compile-time constants.

ui/gfx/geometry/insets_f.h

Index: ui/gfx/geometry/insets_f.h
diff --git a/ui/gfx/geometry/insets_f.h b/ui/gfx/geometry/insets_f.h
index 7ff2cec2e28f26ca7d390360f6d739b46153ab17..30c2ff2b79ae05aeb87e8daa348b93b8c72d6ddd 100644
--- a/ui/gfx/geometry/insets_f.h
+++ b/ui/gfx/geometry/insets_f.h
@@ -14,25 +14,29 @@ namespace gfx {
 // A floating point version of gfx::Insets.
 class GFX_EXPORT InsetsF {
  public:
-  InsetsF();
-  explicit InsetsF(float all);
-  InsetsF(float vertical, float horizontal);
-  InsetsF(float top, float left, float bottom, float right);
-
-  ~InsetsF();
-
-  float top() const { return top_; }
-  float left() const { return left_; }
-  float bottom() const { return bottom_; }
-  float right() const { return right_; }
+  constexpr InsetsF() : top_(0.f), left_(0.f), bottom_(0.f), right_(0.f) {}
+  constexpr explicit InsetsF(float all)
+      : top_(all), left_(all), bottom_(all), right_(all) {}
+  constexpr InsetsF(float vertical, float horizontal)
+      : top_(vertical),
+        left_(horizontal),
+        bottom_(vertical),
+        right_(horizontal) {}
+  constexpr InsetsF(float top, float left, float bottom, float right)
+      : top_(top), left_(left), bottom_(bottom), right_(right) {}
+
+  constexpr float top() const { return top_; }
+  constexpr float left() const { return left_; }
+  constexpr float bottom() const { return bottom_; }
+  constexpr float right() const { return right_; }
 
   // Returns the total width taken up by the insets, which is the sum of the
   // left and right insets.
-  float width() const { return left_ + right_; }
+  constexpr float width() const { return left_ + right_; }
 
   // Returns the total height taken up by the insets, which is the sum of the
   // top and bottom insets.
-  float height() const { return top_ + bottom_; }
+  constexpr float height() const { return top_ + bottom_; }
 
   // Returns true if the insets are empty.
   bool IsEmpty() const { return width() == 0.f && height() == 0.f; }
@@ -60,6 +64,13 @@ class GFX_EXPORT InsetsF {
     right_ += insets.right_;
   }
 
+  void operator-=(const InsetsF& insets) {
+    top_ -= insets.top_;
+    left_ -= insets.left_;
+    bottom_ -= insets.bottom_;
+    right_ -= insets.right_;
+  }
+
   InsetsF operator-() const {
     return InsetsF(-top_, -left_, -bottom_, -right_);
   }
@@ -74,6 +85,16 @@ class GFX_EXPORT InsetsF {
   float right_;
 };
 
+inline InsetsF operator+(InsetsF lhs, const InsetsF& rhs) {
+  lhs += rhs;
+  return lhs;
+}
+
+inline InsetsF operator-(InsetsF lhs, const InsetsF& rhs) {
+  lhs -= rhs;
+  return lhs;
+}
+
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_INSETS_F_H_