Fix string assert and dead code which caused it.

src/core/SkString.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkString.h"
@@ skipping 571 matching lines @@
 
     this->prepend(buffer, strlen(buffer));
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkString::remove(size_t offset, size_t length) {
     size_t size = this->size();
 
     if (offset < size) {
-        if (offset + length > size) {
+        if (length > size - offset) {
             length = size - offset;
         }
+        SkASSERT(length <= size);
+        SkASSERT(offset <= size - length);
         if (length > 0) {
-            SkASSERT(size > length);
             SkString    tmp(size - length);
             char*       dst = tmp.writable_str();
             const char* src = this->c_str();
 
             if (offset) {
-                SkASSERT(offset <= tmp.size());
                 memcpy(dst, src, offset);
             }
-            size_t tail = size - offset - length;
-            SkASSERT((int32_t)tail >= 0);
+            size_t tail = size - (offset + length);
             if (tail) {
-        //      SkASSERT(offset + length <= tmp.size());
-                memcpy(dst + offset, src + offset + length, tail);
+                memcpy(dst + offset, src + (offset + length), tail);
             }
             SkASSERT(dst[tmp.size()] == 0);
             this->swap(tmp);
         }
     }
 }
 
 void SkString::swap(SkString& other) {
     this->validate();
     other.validate();
@@ skipping 21 matching lines @@
         const size_t len = strcspn(str, delimiters);
         out->push_back().set(str, len);
         str += len;
         // Skip any delimiters.
         str += strspn(str, delimiters);
     }
 }
 
 #undef VSNPRINTF
 #undef SNPRINTF