Revert of Try to use only std::aligned_storage. (patchset #2 id:20001 of https://codereview.chromium.org/2468243002/ )

Reason for revert:
DM failure: https://luci-milo.appspot.com/swarming/task/324387bf30100f10

c:\b\work\skia\src\core\sklinearbitmappipeline.cpp:49: fatal error: "assert(sizeof(Variant) <= sizeof(fSpace))"

Original issue's description:
> Try to use only std::aligned_storage. This does not change the API.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2468243002
> TBR=reed@google.com
>
> Committed: https://skia.googlesource.com/skia/+/e736e0c2d52a29a3b88a29ab39b3a90a5a2443a0

TBR=mtklein@chromium.org,bsalomon@google.com,mtklein@google.com,reed@google.com,herb@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2474073002

3 files changed, 26 insertions, 12 deletions

diff --git a/include/core/SkPostConfig.h b/include/core/SkPostConfig.h
index c34397cde6..1b1cb3e751 100644
--- a/include/core/SkPostConfig.h
+++ b/include/core/SkPostConfig.h
@@ -77,6 +77,15 @@
 #  endif
 #endif
 
+// As usual, there are two ways to increase alignment... the MSVC way and the everyone-else way.
+#ifndef SK_STRUCT_ALIGN
+    #ifdef _MSC_VER
+        #define SK_STRUCT_ALIGN(N) __declspec(align(N))
+    #else
+        #define SK_STRUCT_ALIGN(N) __attribute__((aligned(N)))
+    #endif
+#endif
+
 #if defined(_MSC_VER) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
     #define SK_VECTORCALL __vectorcall
 #elif defined(SK_CPU_ARM32) && defined(SK_ARM_HAS_NEON)
diff --git a/src/core/SkLinearBitmapPipeline.h b/src/core/SkLinearBitmapPipeline.h
index d9fa97522e..91b573df5d 100644
--- a/src/core/SkLinearBitmapPipeline.h
+++ b/src/core/SkLinearBitmapPipeline.h
@@ -57,9 +57,6 @@ public:
     void shadeSpan4f(int x, int y, SkPM4f* dst, int count);
     void blitSpan(int32_t x, int32_t y, void* dst, int count);
 
-    template <size_t N>
-    using Storage = typename std::aligned_storage<N, 16>::type;
-
     template<typename Base, size_t kSize, typename Next = void>
     class Stage {
     public:
@@ -87,8 +84,11 @@ public:
 
     private:
         std::function<void (Next*, void*)> fStageCloner;
-        mutable Storage<kSize>             fSpace;
-        bool                               fIsInitialized;
+        struct SK_STRUCT_ALIGN(16) Space {
+            char space[kSize];
+        };
+        bool fIsInitialized;
+        mutable Space fSpace;
     };
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -116,8 +116,11 @@ public:
         Base& operator*() const { return *(this->get()); }
 
     private:
-        mutable Storage<kSize> fSpace;
-        bool                   fIsInitialized;
+        struct SK_STRUCT_ALIGN(16) Space {
+            char space[kSize];
+        };
+        mutable Space fSpace;
+        bool          fIsInitialized;
 
     };
 
diff --git a/src/core/SkSmallAllocator.h b/src/core/SkSmallAllocator.h
index b39e359d52..9095fa57fc 100644
--- a/src/core/SkSmallAllocator.h
+++ b/src/core/SkSmallAllocator.h
@@ -93,7 +93,7 @@ public:
             // There is space in fStorage.
             rec->fStorageSize = storageRequired;
             rec->fHeapStorage = nullptr;
-            rec->fObj = static_cast<void*>(bytes() + fStorageUsed);
+            rec->fObj = static_cast<void*>(fStorage.fBytes + fStorageUsed);
             fStorageUsed += storageRequired;
         }
         rec->fKillProc = DestroyT<T>;
@@ -129,11 +129,13 @@ private:
         static_cast<T*>(ptr)->~T();
     }
 
-    char* bytes() { return reinterpret_cast<char*>(&fStorage); }
-
-    using Storage = typename std::aligned_storage<kTotalBytes, 16>::type;
+    struct SK_STRUCT_ALIGN(16) Storage {
+        // we add kMaxObjects * 15 to account for the worst-case slop, where each allocation wasted
+        // 15 bytes (due to forcing each to be 16-byte aligned)
+        char    fBytes[kTotalBytes + kMaxObjects * 15];
+    };
 
-    Storage     fStorage[kMaxObjects];
+    Storage     fStorage;
     // Number of bytes used so far.
     size_t      fStorageUsed;
     uint32_t    fNumObjects;