Introduce ui.dll / libui.so for the component build.

ui/gfx/size.h

Index: ui/gfx/size.h
===================================================================
--- ui/gfx/size.h	(revision 92815)
+++ ui/gfx/size.h	(working copy)
@@ -6,10 +6,11 @@
 #define UI_GFX_SIZE_H_
 #pragma once
 
+#include <iosfwd>
+
 #include "build/build_config.h"
+#include "ui/ui_api.h"
 
-#include <iosfwd>
-
 #if defined(OS_WIN)
 typedef struct tagSIZE SIZE;
 #elif defined(OS_MACOSX)
@@ -19,7 +20,7 @@
 namespace gfx {
 
 // A size has width and height values.
-class Size {
+class UI_API Size {
  public:
   Size() : width_(0), height_(0) {}
   Size(int width, int height);
@@ -75,7 +76,7 @@
   int height_;
 };
 
-std::ostream& operator<<(std::ostream& out, const gfx::Size& s);
+UI_API std::ostream& operator<<(std::ostream& out, const gfx::Size& s);
 
 }  // namespace gfx