Fixed compiler warning C4267 'conversion from 'size_t' to 'type', possible loss of data'

BUG=angleproject:1120

Change-Id: I01ef10bea7f487c2b394d030c76628f38d2ea645
Reviewed-on: https://chromium-review.googlesource.com/292780
Tested-by: Cooper Partin <coopp@microsoft.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/Buffer.cpp b/src/libANGLE/Buffer.cpp
index 451ff5b..4dca1c9 100644
--- a/src/libANGLE/Buffer.cpp
+++ b/src/libANGLE/Buffer.cpp
@@ -162,7 +162,8 @@
 
 Error Buffer::getIndexRange(GLenum type, size_t offset, size_t count, gl::RangeUI *outRange) const
 {
-    if (mIndexRangeCache.findRange(type, offset, count, outRange))
+    if (mIndexRangeCache.findRange(type, static_cast<unsigned int>(offset),
+                                   static_cast<GLsizei>(count), outRange))
     {
         return gl::Error(GL_NO_ERROR);
     }
@@ -173,7 +174,8 @@
         return error;
     }
 
-    mIndexRangeCache.addRange(type, offset, count, *outRange);
+    mIndexRangeCache.addRange(type, static_cast<unsigned int>(offset), static_cast<GLsizei>(count),
+                              *outRange);
 
     return Error(GL_NO_ERROR);
 }