Validate text blob runs after SkTextBlob construction.

src/core/SkTextBlob.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTextBlob.h"
 
 #include "SkReadBuffer.h"
@@ skipping 139 matching lines @@
     static const RunRecord* First(const SkTextBlob* blob) {
         // The first record (if present) is stored following the blob object.
         return reinterpret_cast<const RunRecord*>(blob + 1);
     }
 
     static const RunRecord* Next(const RunRecord* run) {
         return reinterpret_cast<const RunRecord*>(reinterpret_cast<const uint8_t*>(run)
             + StorageSize(run->glyphCount(), run->positioning()));
     }
 
-    void validate(uint8_t* storageTop) const {
+    void validate(const uint8_t* storageTop) const {
         SkASSERT(kRunRecordMagic == fMagic);
         SkASSERT((uint8_t*)Next(this) <= storageTop);
         SkASSERT(glyphBuffer() + fCount <= (uint16_t*)posBuffer());
         SkASSERT(posBuffer() + fCount * ScalarsPerGlyph(fPositioning) <= (SkScalar*)Next(this));
     }
 
 private:
     friend class SkTextBlobBuilder;
 
     void grow(uint32_t count) {
@@ skipping 405 matching lines @@
     SkASSERT((fRunCount > 0) == (nullptr != fStorage.get()));
 
     this->updateDeferredBounds();
 
     if (0 == fRunCount) {
         SkASSERT(nullptr == fStorage.get());
         fStorageUsed = sizeof(SkTextBlob);
         fStorage.realloc(fStorageUsed);
     }
 
+    const SkTextBlob* blob = new (fStorage.detach()) SkTextBlob(fRunCount, fBounds);
+    SkDEBUGCODE(const_cast<SkTextBlob*>(blob)->fStorageSize = fStorageSize;)
+
     SkDEBUGCODE(
         size_t validateSize = sizeof(SkTextBlob);
-        const SkTextBlob::RunRecord* run =
-            SkTextBlob::RunRecord::First(reinterpret_cast<const SkTextBlob*>(fStorage.get()));
+        const SkTextBlob::RunRecord* run = SkTextBlob::RunRecord::First(blob);
         for (int i = 0; i < fRunCount; ++i) {
             validateSize += SkTextBlob::RunRecord::StorageSize(run->fCount, run->fPositioning);
-            run->validate(fStorage.get() + fStorageUsed);
+            run->validate(reinterpret_cast<const uint8_t*>(blob) + fStorageUsed);
             run = SkTextBlob::RunRecord::Next(run);
         }
         SkASSERT(validateSize == fStorageUsed);
     )
 
-    const SkTextBlob* blob = new (fStorage.detach()) SkTextBlob(fRunCount, fBounds);
-    SkDEBUGCODE(const_cast<SkTextBlob*>(blob)->fStorageSize = fStorageSize;)
-
     fStorageUsed = 0;
     fStorageSize = 0;
     fRunCount = 0;
     fLastRun = 0;
     fBounds.setEmpty();
 
     return blob;
 }