Allow 0-width SkBitmap in setConfig.

Previously, SkBitmap::setConfig would allow zero height, but not zero
width.  This is changed for consistancy.

A unit test was added.

BUG=
R=reed@google.com, scroggo@google.com

Review URL: https://codereview.chromium.org/111953004

git-svn-id: http://skia.googlecode.com/svn/trunk@12673 2bbb7eff-a529-9590-31e7-b0007b416f81

gyp/tests.gyp

@@ -32,6 +32,7 @@
         '../tests/AnnotationTest.cpp',
         '../tests/ARGBImageEncoderTest.cpp',
         '../tests/AtomicTest.cpp',
+        '../tests/BitmapTest.cpp',
         '../tests/BitmapCopyTest.cpp',
         '../tests/BitmapGetColorTest.cpp',
         '../tests/BitmapHasherTest.cpp',

src/core/SkBitmap.cpp

@@ -298,7 +298,7 @@ bool SkBitmap::setConfig(Config config, int width, int height, size_t rowBytes,
     }
     if (rowBytes == 0) {
         rowBytes = SkBitmap::ComputeRowBytes(config, width);
-        if (0 == rowBytes && kNo_Config != config) {
+        if (0 == rowBytes && kNo_Config != config && width > 0) {
             goto BAD_CONFIG;
         }
     }

tests/BitmapTest.cpp

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmap.h"
+
+#include "Test.h"
+#include "TestClassDef.h"
+
+/**
+ *  This test contains basic sanity checks concerning bitmaps.
+ */
+DEF_TEST(Bitmap, reporter) {
+    const SkBitmap::Config conf = SkBitmap::kARGB_8888_Config;
+    // Zero-sized bitmaps are allowed
+    for (int width = 0; width < 2; ++width) {
+        for (int height = 0; height < 2; ++height) {
+            SkBitmap bm;
+            bool setConf = bm.setConfig(conf, width, height);
+            REPORTER_ASSERT(reporter, setConf);
+            if (setConf) {
+                REPORTER_ASSERT(reporter, bm.allocPixels(NULL));
+            }
+            REPORTER_ASSERT(reporter, (width & height) != bm.empty());
+        }
+    }
+}