Fix cases of variable shadowing in samplecode/.

These were reviewed last year at http://review.skia.org/312480 but never
landed. Splitting into small chunks to land individually.

If we manage to fix all the existing cases of variable shadowing, we
could enable -Wshadow.

Change-Id: I53d04e5b2ffd7e170a8b10a6bacbc239c8b5e7ff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/435720
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ravi Mistry <rmistry@google.com>
diff --git a/samplecode/SampleXfermodesBlur.cpp b/samplecode/SampleXfermodesBlur.cpp
index c135821..bd603d5 100644
--- a/samplecode/SampleXfermodesBlur.cpp
+++ b/samplecode/SampleXfermodesBlur.cpp
@@ -104,7 +104,7 @@
         font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
         setNamedTypeface(&font, "Menlo Regular");
 
-        const int W = 5;
+        const int kWrap = 5;
 
         SkScalar x0 = 0;
         for (int twice = 0; twice < 2; twice++) {
@@ -131,7 +131,7 @@
                 SkTextUtils::DrawString(canvas, label, x + w/2, y - font.getSize()/2, font, SkPaint(),
                                         SkTextUtils::kCenter_Align);
                 x += w + SkIntToScalar(10);
-                if ((i % W) == W - 1) {
+                if ((i % kWrap) == kWrap - 1) {
                     x = x0;
                     y += h + SkIntToScalar(30);
                 }