Add compile assertions to enforce the sizes of all structs and enums in the C API.  Adjust some structs to make their sizes consistent across architectures.  Note that some structs contain pointers, so are difficult to make consistent between 32-bit and 64-bit.  Those types are in test_struct_sizes.c.  Other types have a compile assertion immediately after their definition.

This was broken off from a bigger CL:
http://codereview.chromium.org/5340003/

BUG=61004,92983
TEST=test_struct_sizes.c, compile assertions throughout

See this CL for the code that helped generate the static assertions and find affected interfaces:
http://codereview.chromium.org/5730003
Review URL: http://codereview.chromium.org/5674004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@69038 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ppapi/c/pp_point.h b/ppapi/c/pp_point.h
index 0ff85621..675a5522 100644
--- a/ppapi/c/pp_point.h
+++ b/ppapi/c/pp_point.h
@@ -20,6 +20,7 @@
   int32_t x;
   int32_t y;
 };
+PP_COMPILE_ASSERT_STRUCT_SIZE_IN_BYTES(PP_Point, 8);
 
 PP_INLINE struct PP_Point PP_MakePoint(int32_t x, int32_t y) {
   struct PP_Point ret;