Make SkSmallAllocator obey the RAII invariants and be expandable

src/core/SkBlitter.cpp

Index: src/core/SkBlitter.cpp
diff --git a/src/core/SkBlitter.cpp b/src/core/SkBlitter.cpp
index 3643e667601d2b8a60c0ee4e4000d56f541a7a0c..8f5973c851a105d94589c1426544b45bff08fac1 100644
--- a/src/core/SkBlitter.cpp
+++ b/src/core/SkBlitter.cpp
@@ -896,14 +896,15 @@ SkBlitter* SkBlitter::Choose(const SkPixmap& device,
         size_t contextSize = shader->contextSize(rec);
         if (contextSize) {
             // Try to create the ShaderContext
-            void* storage = allocator->reserveT<SkShader::Context>(contextSize);
-            shaderContext = shader->createContext(rec, storage);
+            shaderContext = allocator->createWithIniterT<SkShader::Context>(
+                contextSize,
+                [&rec, shader](void* storage) {
+                    return shader->createContext(rec, storage);
+                });
             if (!shaderContext) {
-                allocator->freeLast();
                 return allocator->createT<SkNullBlitter>();
             }
             SkASSERT(shaderContext);
-            SkASSERT((void*) shaderContext == storage);
         } else {
             return allocator->createT<SkNullBlitter>();
         }