The HLSL compiler can optimize out the last elements of a struct, which caused ANGLE to overwrite constants right after the end of the struct. Each element in a struct should be limited by the size of the entire struct.

BUG=

Review URL: https://codereview.appspot.com/6856100

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1564 736b8ea6-26fd-11df-bfd4-992fa37f6226