Reland "Add format-specifier warnings to SkDebugf."

This is a reland of e58831cd9578805634b986b434a20757277b3a36

Original change's description:
> Add format-specifier warnings to SkDebugf.
>
> This CL fixes up many existing format-specifier violations in Skia.
> Note that GCC has a warning for formatting nothing, so existing calls to
> `SkDebugf("")` have been removed, or replaced with `SkDebugf("%s", "")`.
> These were apparently meant to be used as a place to set a breakpoint.
>
> Some of our clients also use SkDebug with bad format specifiers, so this
> check is currently only enabled when SKIA_IMPLEMENTATION is true.
>
> Change-Id: I8177a1298a624c6936adc24e0d8f481362a356d0
> Bug: skia:12143
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/420902
> Auto-Submit: John Stiles <johnstiles@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:12143
Change-Id: Id3c0c21436ebd13899908d5ed5d44c42a0e23921
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/421918
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/docs/examples/Pixmap_rowBytes.cpp b/docs/examples/Pixmap_rowBytes.cpp
index 4cffbec..71a0abe 100644
--- a/docs/examples/Pixmap_rowBytes.cpp
+++ b/docs/examples/Pixmap_rowBytes.cpp
@@ -7,7 +7,7 @@
     SkPixmap badPixmap = {SkImageInfo::MakeA8(4, 4), nullptr, 2};
     SkPixmap okPixmap = {SkImageInfo::MakeA8(4, 4), nullptr, 8};
     for (auto& pixmap : { badPixmap, okPixmap } ) {
-        SkDebugf("rowBytes: %d minRowBytes: %d\n", pixmap.rowBytes(),
+        SkDebugf("rowBytes: %zu minRowBytes: %zu\n", pixmap.rowBytes(),
            pixmap.info().minRowBytes());
     }
 }