Fix signed/unsigned comparison mismatch

mojo/android/system/core_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/android/system/core_impl.h"
 
 #include "base/android/base_jni_registrar.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_registrar.h"
 #include "base/android/library_loader/library_loader_hooks.h"
@@ skipping 145 matching lines @@
                  jobject jcaller,
                  jobject buffer,
                  jint mojo_handle,
                  jint signals,
                  jlong deadline) {
   // Buffer contains space for the MojoHandleSignalsState
   void* buffer_start = env->GetDirectBufferAddress(buffer);
   DCHECK(buffer_start);
   DCHECK_EQ(reinterpret_cast<const uintptr_t>(buffer_start) % 8, 0u);
   DCHECK_EQ(sizeof(struct MojoHandleSignalsState),
-            env->GetDirectBufferCapacity(buffer));
+            static_cast<size_t>(env->GetDirectBufferCapacity(buffer)));
   struct MojoHandleSignalsState* signals_state =
       static_cast<struct MojoHandleSignalsState*>(buffer_start);
   return MojoWait(mojo_handle, signals, deadline, signals_state);
 }
 
 static jint WriteMessage(JNIEnv* env,
                          jobject jcaller,
                          jint mojo_handle,
                          jobject bytes,
                          jint num_bytes,
@@ skipping 217 matching lines @@
       reinterpret_cast<AsyncWaitCallbackData*>(data_ptr));
   Environment::GetDefaultAsyncWaiter()->CancelWait(id);
 }
 
 bool RegisterCoreImpl(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace mojo