Add explicit integer casts

WebKit uses the -Wshorten-64-to-32 flag which warns on these cases.

Bug: 3439
Change-Id: I8c1de60da0f173ca2036e2120e79b857f5f2775f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1740866
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>

samples/sample_util/SampleApplication.cpp

@@ -47,8 +47,8 @@ SampleApplication::SampleApplication(std::string name,
                                      char **argv,
                                      EGLint glesMajorVersion,
                                      EGLint glesMinorVersion,
-                                     size_t width,
-                                     size_t height)
+                                     uint32_t width,
+                                     uint32_t height)
     : mName(std::move(name)),
       mWidth(width),
       mHeight(height),