add SkCanvas::NewRaster factory -- a very common use-case in chrome

BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/183533004

git-svn-id: http://skia.googlecode.com/svn/trunk@13617 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/CanvasTest.cpp b/tests/CanvasTest.cpp
index 5f3d79c..18c683d 100644
--- a/tests/CanvasTest.cpp
+++ b/tests/CanvasTest.cpp
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2012 Google Inc.
  *
@@ -893,6 +892,45 @@
     }
 }
 
+static void test_newraster(skiatest::Reporter* reporter) {
+    SkImageInfo info = SkImageInfo::MakeN32Premul(10, 10);
+    SkCanvas* canvas = SkCanvas::NewRaster(info);
+    REPORTER_ASSERT(reporter, canvas);
+
+    SkImageInfo info2;
+    size_t rowBytes;
+    const SkPMColor* addr = (const SkPMColor*)canvas->peekPixels(&info2, &rowBytes);
+    REPORTER_ASSERT(reporter, addr);
+    REPORTER_ASSERT(reporter, info == info2);
+    for (int y = 0; y < info.height(); ++y) {
+        for (int x = 0; x < info.width(); ++x) {
+            REPORTER_ASSERT(reporter, 0 == addr[x]);
+        }
+        addr = (const SkPMColor*)((const char*)addr + rowBytes);
+    }
+    SkDELETE(canvas);
+
+    // now try a deliberately bad info
+    info.fWidth = -1;
+    REPORTER_ASSERT(reporter, NULL == SkCanvas::NewRaster(info));
+
+    // too big
+    info.fWidth = 1 << 30;
+    info.fHeight = 1 << 30;
+    REPORTER_ASSERT(reporter, NULL == SkCanvas::NewRaster(info));
+    
+    // not a valid pixel type
+    info.fWidth = info.fHeight = 10;
+    info.fColorType = kUnknown_SkColorType;
+    REPORTER_ASSERT(reporter, NULL == SkCanvas::NewRaster(info));
+
+    // We should succeed with a zero-sized valid info
+    info = SkImageInfo::MakeN32Premul(0, 0);
+    canvas = SkCanvas::NewRaster(info);
+    REPORTER_ASSERT(reporter, canvas);
+    SkDELETE(canvas);
+}
+
 DEF_TEST(Canvas, reporter) {
     // Init global here because bitmap pixels cannot be alocated during
     // static initialization
@@ -909,4 +947,6 @@
 
     // Explicitly call reset(), so we don't leak the pixels (since kTestBitmap is a global)
     kTestBitmap.reset();
+
+    test_newraster(reporter);
 }
diff --git a/tests/DrawPathTest.cpp b/tests/DrawPathTest.cpp
index f7f7367..fafef02 100644
--- a/tests/DrawPathTest.cpp
+++ b/tests/DrawPathTest.cpp
@@ -11,14 +11,6 @@
 #include "SkSurface.h"
 #include "Test.h"
 
-static SkCanvas* new_canvas(int w, int h) {
-    SkBitmap bm;
-    bm.allocN32Pixels(w, h);
-    return new SkCanvas(bm);
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
 // test that we can draw an aa-rect at coordinates > 32K (bigger than fixedpoint)
 static void test_big_aa_rect(skiatest::Reporter* reporter) {
     SkBitmap output;
@@ -103,7 +95,7 @@
     moveToH(&path, &data[0]);
     cubicToH(&path, &data[2]);
 
-    SkAutoTUnref<SkCanvas> canvas(new_canvas(640, 480));
+    SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterN32(640, 480));
 
     SkPaint paint;
     paint.setAntiAlias(true);
@@ -141,7 +133,7 @@
 
     SkPaint paint;
 
-    SkAutoTUnref<SkCanvas> canvas(new_canvas(640, 480));
+    SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterN32(640, 480));
     canvas.get()->save();
     canvas.get()->clipRect(SkRect::MakeWH(SkIntToScalar(19), SkIntToScalar(11)));
 
@@ -181,7 +173,7 @@
     SkPaint paint;
     paint.setAntiAlias(true);
 
-    SkAutoTUnref<SkCanvas> canvas(new_canvas(640, 480));
+    SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterN32(640, 480));
     canvas.get()->drawPath(path, paint);
 }
 
@@ -223,7 +215,7 @@
     SkPaint paint;
     paint.setAntiAlias(true);
 
-    SkAutoTUnref<SkCanvas> canvas(new_canvas(640, 480));
+    SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterN32(640, 480));
     canvas.get()->drawPath(path, paint);
 }
 
@@ -233,8 +225,7 @@
 static void test_giantaa() {
     const int W = 400;
     const int H = 400;
-    SkAutoTUnref<SkCanvas> canvas(new_canvas(33000, 10));
-    canvas.get()->clear(SK_ColorTRANSPARENT);
+    SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterN32(33000, 10));
 
     SkPaint paint;
     paint.setAntiAlias(true);