Fix and enable warning C4244 (Conversion from 'type1' to 'type2', possible loss of data)

Change-Id: Id0e06d7d6600344d858f00dabc219d79289bbc82
Reviewed-on: https://chromium-review.googlesource.com/265020
Tested-by: Minmin Gong <mgong@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 5ea039f..341f7e3 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -339,7 +339,7 @@
     // wait commands finish. However, since the name becomes invalid, we cannot query the fence,
     // and since our API is currently designed for being called from a single thread, we can delete
     // the fence immediately.
-    mResourceManager->deleteFenceSync(reinterpret_cast<uintptr_t>(fenceSync));
+    mResourceManager->deleteFenceSync(static_cast<GLuint>(reinterpret_cast<uintptr_t>(fenceSync)));
 }
 
 void Context::deleteVertexArray(GLuint vertexArray)
@@ -445,7 +445,7 @@
 
 FenceSync *Context::getFenceSync(GLsync handle) const
 {
-    return mResourceManager->getFenceSync(reinterpret_cast<uintptr_t>(handle));
+    return mResourceManager->getFenceSync(static_cast<GLuint>(reinterpret_cast<uintptr_t>(handle)));
 }
 
 VertexArray *Context::getVertexArray(GLuint handle) const