Enable size_t to int truncation warnings in PPAPI

ppapi/proxy/platform_verification_private_resource.cc

Index: ppapi/proxy/platform_verification_private_resource.cc
diff --git a/ppapi/proxy/platform_verification_private_resource.cc b/ppapi/proxy/platform_verification_private_resource.cc
index 76d514871d0c39cd4638a939a9a9aadd03866b6a..27804d36dc90ffa4875794111531cb81a6daca36 100644
--- a/ppapi/proxy/platform_verification_private_resource.cc
+++ b/ppapi/proxy/platform_verification_private_resource.cc
@@ -88,10 +88,11 @@ void PlatformVerificationPrivateResource::OnChallengePlatformReply(
   if (params.result() == PP_OK) {
     *(output_params.signed_data) =
         (PpapiGlobals::Get()->GetVarTracker()->MakeArrayBufferVar(
-            raw_signed_data.size(), &raw_signed_data.front()))->GetPPVar();
+            static_cast<uint32_t>(raw_signed_data.size()),
+            &raw_signed_data.front()))->GetPPVar();
     *(output_params.signed_data_signature) =
         (PpapiGlobals::Get()->GetVarTracker()->MakeArrayBufferVar(
-            raw_signed_data_signature.size(),
+            static_cast<uint32_t>(raw_signed_data_signature.size()),
             &raw_signed_data_signature.front()))->GetPPVar();
     *(output_params.platform_key_certificate) =
         (new StringVar(raw_platform_key_certificate))->GetPPVar();