Change Size::IsEmpty() to be consistent with Rect::IsEmpty()

base/gfx/size.cc

Index: base/gfx/size.cc
===================================================================
--- base/gfx/size.cc	(revision 14559)
+++ base/gfx/size.cc	(working copy)
@@ -10,8 +10,16 @@
 #include <CoreGraphics/CGGeometry.h>
 #endif
 
+#include "base/logging.h"
+
+
 namespace gfx {
 
+Size::Size(int width, int height) {
+  set_width(width);
+  set_height(height);
+}
+
 #if defined(OS_WIN)
 SIZE Size::ToSIZE() const {
   SIZE s;
@@ -25,4 +33,21 @@
 }
 #endif
 
+void Size::set_width(int width) {
+  if (width < 0) {
+    NOTREACHED();
+    width = 0;
+  }
+  width_ = width;
+}
+
+void Size::set_height(int height) {
+  if (height < 0) {
+    NOTREACHED();
+    height = 0;
+  }
+  height_ = height;
+}
+
+
 }  // namespace gfx