Make SkSmallAllocator obey the RAII invariants and be expandable

tests/LayerDrawLooperTest.cpp

 /*
  * 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 "SkBitmapDevice.h"
 #include "SkCanvas.h"
@@ skipping 42 matching lines @@
     layerInfo.fOffset.set(10.0f, 20.0f);
     layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
     SkPaint* layerPaint = looperBuilder.addLayer(layerInfo);
     layerPaint->setBlendMode(SkBlendMode::kSrc);
 
     FakeDevice device;
     SkCanvas canvas(&device);
     SkPaint paint;
     auto looper(looperBuilder.detach());
     SkSmallAllocator<1, 32> allocator;
-    void* buffer = allocator.reserveT<SkDrawLooper::Context>(looper->contextSize());
-    SkDrawLooper::Context* context = looper->createContext(&canvas, buffer);
+    SkDrawLooper::Context* context = allocator.createWithIniter(
+        looper->contextSize(),
+        [&](void* buffer) {
+            return looper->createContext(&canvas, buffer);
+        });
 
     // The back layer should come first.
     REPORTER_ASSERT(reporter, context->next(&canvas, &paint));
     REPORTER_ASSERT(reporter, paint.getBlendMode() == SkBlendMode::kSrc);
     canvas.drawRect(SkRect::MakeWH(50.0f, 50.0f), paint);
     REPORTER_ASSERT(reporter, 10.0f == device.fLastMatrix.getTranslateX());
     REPORTER_ASSERT(reporter, 20.0f == device.fLastMatrix.getTranslateY());
     paint.reset();
 
     // Then the front layer.
@@ skipping 18 matching lines @@
     layerInfo.fOffset.set(10.0f, 20.0f);
     layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
     SkPaint* layerPaint = looperBuilder.addLayerOnTop(layerInfo);
     layerPaint->setBlendMode(SkBlendMode::kSrc);
 
     FakeDevice device;
     SkCanvas canvas(&device);
     SkPaint paint;
     auto looper(looperBuilder.detach());
     SkSmallAllocator<1, 32> allocator;
-    void* buffer = allocator.reserveT<SkDrawLooper::Context>(looper->contextSize());
-    SkDrawLooper::Context* context = looper->createContext(&canvas, buffer);
+    SkDrawLooper::Context* context = allocator.createWithIniter(
+        looper->contextSize(),
+        [&](void* buffer) {
+            return looper->createContext(&canvas, buffer);
+        });
 
     // The back layer should come first.
     REPORTER_ASSERT(reporter, context->next(&canvas, &paint));
     REPORTER_ASSERT(reporter, paint.getBlendMode() == SkBlendMode::kSrcOver);
     canvas.drawRect(SkRect::MakeWH(50.0f, 50.0f), paint);
     REPORTER_ASSERT(reporter, 0.0f == device.fLastMatrix.getTranslateX());
     REPORTER_ASSERT(reporter, 0.0f == device.fLastMatrix.getTranslateY());
     paint.reset();
 
     // Then the front layer.
@@ skipping 18 matching lines @@
     layerInfo.fOffset.set(10.0f, 20.0f);
     layerInfo.fPaintBits |= SkLayerDrawLooper::kXfermode_Bit;
     SkPaint* layerPaint = looperBuilder.addLayerOnTop(layerInfo);
     layerPaint->setBlendMode(SkBlendMode::kSrc);
 
     FakeDevice device;
     SkCanvas canvas(&device);
     SkPaint paint;
     sk_sp<SkDrawLooper> looper(looperBuilder.detach());
     SkSmallAllocator<1, 32> allocator;
-    void* buffer = allocator.reserveT<SkDrawLooper::Context>(looper->contextSize());
-    SkDrawLooper::Context* context = looper->createContext(&canvas, buffer);
+    SkDrawLooper::Context* context = allocator.createWithIniter(
+        looper->contextSize(),
+        [&](void* buffer) {
+            return looper->createContext(&canvas, buffer);
+        });
 
     // The back layer should come first.
     REPORTER_ASSERT(reporter, context->next(&canvas, &paint));
     REPORTER_ASSERT(reporter, paint.getBlendMode() == SkBlendMode::kSrcOver);
     canvas.drawRect(SkRect::MakeWH(50.0f, 50.0f), paint);
     REPORTER_ASSERT(reporter, 0.0f == device.fLastMatrix.getTranslateX());
     REPORTER_ASSERT(reporter, 0.0f == device.fLastMatrix.getTranslateY());
     paint.reset();
 
     // Then the front layer.
     REPORTER_ASSERT(reporter, context->next(&canvas, &paint));
     REPORTER_ASSERT(reporter, paint.getBlendMode() == SkBlendMode::kSrc);
     canvas.drawRect(SkRect::MakeWH(50.0f, 50.0f), paint);
     REPORTER_ASSERT(reporter, 10.0f == device.fLastMatrix.getTranslateX());
     REPORTER_ASSERT(reporter, 20.0f == device.fLastMatrix.getTranslateY());
 
     // Only two layers were added, so that should be the end.
     REPORTER_ASSERT(reporter, !context->next(&canvas, &paint));
 }
 
 DEF_TEST(LayerDrawLooper, reporter) {
     test_frontToBack(reporter);
     test_backToFront(reporter);
     test_mixed(reporter);
 }