Adds support for saving favicon size into history database.

ui/gfx/size_base.h

Index: ui/gfx/size_base.h
diff --git a/ui/gfx/size_base.h b/ui/gfx/size_base.h
index f8373e8a802f79984fb1b4c9dae91616084fdaf1..44695d2b09318980e18bfe315f3a012362127bf1 100644
--- a/ui/gfx/size_base.h
+++ b/ui/gfx/size_base.h
@@ -51,6 +51,15 @@ class UI_EXPORT SizeBase {
     return !(*this == s);
   }
 
+  // A size is less than another size if its width is less than the |other|
+  // size's width. If the widths are equal, then the size with the smallest
+  // height is less than the other. The comparison is required to uses Sizes in
+  // sets and sorted vectors.
+  bool operator<(const Class& other) const {
+    return (width_ == other.width_) ?
+        height_ < other.height_ : width_ < other.width_;
+  }
+
   bool IsEmpty() const {
     // Size doesn't allow negative dimensions, so testing for 0 is enough.
     return (width_ == 0) || (height_ == 0);