Fix windows compile: fix size_t vs. int mismatch

As indicated by:
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_rel_ng/builds/63417/steps/compile%20%28with%20patch%29/logs/stdio

R=thestig@chromium.org
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1160293003
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index d5bf3c0..da33f80 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -582,9 +582,11 @@
   v8::Platform* platform = v8::platform::CreateDefaultPlatform();
   v8::V8::InitializePlatform(platform);
   v8::V8::Initialize();
-  // By enabling predicatble mode, V8 won't post any background tasks.
-  const char predictable_flag[] = "--predictable";
-  v8::V8::SetFlagsFromString(predictable_flag, strlen(predictable_flag));
+
+  // By enabling predictable mode, V8 won't post any background tasks.
+  static const char predictable_flag[] = "--predictable";
+  v8::V8::SetFlagsFromString(predictable_flag,
+                             static_cast<int>(strlen(predictable_flag)));
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
   v8::StartupData natives;