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/Renderbuffer.cpp b/src/libANGLE/Renderbuffer.cpp
index eb6357e..02e067c 100644
--- a/src/libANGLE/Renderbuffer.cpp
+++ b/src/libANGLE/Renderbuffer.cpp
@@ -44,8 +44,8 @@
         return error;
     }
 
-    mWidth = width;
-    mHeight = height;
+    mWidth          = static_cast<GLsizei>(width);
+    mHeight         = static_cast<GLsizei>(height);
     mInternalFormat = internalformat;
     mSamples = 0;
 
@@ -62,10 +62,10 @@
         return error;
     }
 
-    mWidth = width;
-    mHeight = height;
+    mWidth          = static_cast<GLsizei>(width);
+    mHeight         = static_cast<GLsizei>(height);
     mInternalFormat = internalformat;
-    mSamples = samples;
+    mSamples        = static_cast<GLsizei>(samples);
 
     return Error(GL_NO_ERROR);
 }
@@ -82,8 +82,8 @@
 
     setTargetImage(image);
 
-    mWidth          = image->getWidth();
-    mHeight         = image->getHeight();
+    mWidth          = static_cast<GLsizei>(image->getWidth());
+    mHeight         = static_cast<GLsizei>(image->getHeight());
     mInternalFormat = image->getInternalFormat();
     mSamples        = 0;