Fix up some types in the API.

ppapi/proxy/ppb_core_proxy.cc

Index: ppapi/proxy/ppb_core_proxy.cc
diff --git a/ppapi/proxy/ppb_core_proxy.cc b/ppapi/proxy/ppb_core_proxy.cc
index 34993fa8f0e5d10ee7226ecb89f7aad8416512b9..2f8f3e0cf9d13f34c512d89b9a3252f64feb0f08 100644
--- a/ppapi/proxy/ppb_core_proxy.cc
+++ b/ppapi/proxy/ppb_core_proxy.cc
@@ -36,12 +36,12 @@ void ReleaseResource(PP_Resource resource) {
   PluginResourceTracker::GetInstance()->ReleaseResource(resource);
 }
 
-void* MemAlloc(size_t num_bytes) {
+void* MemAlloc(uint32_t num_bytes) {
   return malloc(num_bytes);
 }
 
-void MemFree(void* ptr) {
-  free(ptr);
+void MemFree(const void* ptr) {
+  free(const_cast<void*>(ptr));
 }
 
 double GetTime() {