Fix Windows build warning LNK4217 for blink_platform.dll.

third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h

Index: third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h
diff --git a/third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h b/third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h
index 42afd6604329b13a79a26d14450246c672bb102a..b88c3b20a0e7337c6ae8b10585bb19786cfa653a 100644
--- a/third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h
+++ b/third_party/WebKit/Source/platform/mojo/GeometryStructTraits.h
@@ -5,17 +5,16 @@
 #ifndef GeometryStructTraits_h
 #define GeometryStructTraits_h
 
-#include "platform/PlatformExport.h"
-#include "ui/gfx/geometry/mojo/geometry.mojom-blink.h"
+#include "third_party/WebKit/public/platform/WebSize.h"
+#include "ui/gfx/geometry/mojo/geometry.mojom-shared.h"

[haraken, 2017/01/16 12:31:46]

Would you help me understand what *-shared.h means? How is it different from
*-blink.h?

In general, our convention has been that we only include *-blink.h in Blink.

+esprehn

[leonhsl(Using Gerrit), 2017/01/17 03:40:07]

xxx.mojom-shared.h is included by both xxx.mojom.h and xxx.mojom-blink.h, it
defines xxx::mojom::FooDataView class used by mojo internal
serialization/deserialization process for both xxx::mojom::Foo and
xxx::mojom::blink::Foo, so actually just providing struct traits impl for
xxx::mojom::FooDataView(defined in *-shared.h) is enough to do typemapping for
both Chromium variant and Blink variant. Including xxx.mojom-blink.h instead
would possibly bring in some unnecessary headers/deps. 
I switched to use *-shared.h at ps#5 to address comments from Yuzhu at
https://codereview.chromium.org/2574593003/diff/80001/third_party/WebKit/Sour....

Also, I found some other places in Blink are using *-shared.h in struct traits:
https://cs.chromium.org/search/?q=mojom-shared.h+file:%5Esrc/third_party/WebK...
And actually this CL is doing the similar work with
third_party/WebKit/public/web/window_features.typemap, putting struct traits
impl into a separate source_set target which is declared as a dep by the
xxxx.typemap file.

 
 namespace mojo {
 
 template <>
-struct PLATFORM_EXPORT
-    StructTraits<gfx::mojom::blink::Size::DataView, ::blink::WebSize> {
+struct StructTraits<gfx::mojom::SizeDataView, ::blink::WebSize> {
   static int width(const ::blink::WebSize& size) { return size.width; }
   static int height(const ::blink::WebSize& size) { return size.height; }
-  static bool Read(gfx::mojom::blink::Size::DataView, ::blink::WebSize* out);
+  static bool Read(gfx::mojom::SizeDataView, ::blink::WebSize* out);
 };
 
 }  // namespace mojo