Change growth function for SkWriter32

src/core/SkWriter32.cpp

Index: src/core/SkWriter32.cpp
diff --git a/src/core/SkWriter32.cpp b/src/core/SkWriter32.cpp
index 1e8a10c87caceffa61045fbf1fe0524dfb92ff4e..f1fde893927ab441d9fe9a48a345691620bdd7a4 100644
--- a/src/core/SkWriter32.cpp
+++ b/src/core/SkWriter32.cpp
@@ -67,20 +67,22 @@ size_t SkWriter32::WriteStringSize(const char* str, size_t len) {
     return SkAlign4(lenBytes + len + 1);
 }
 
+const size_t kMinBufferBytes=4096;
+
 void SkWriter32::growToAtLeast(size_t size) {
     bool wasExternal = (fExternal != NULL) && (fData == fExternal);
+    fCapacity = kMinBufferBytes +
+        SkTMax(size, fCapacity + (fCapacity >> 1));
+
     // cause the buffer to grow
-    fInternal.setCount(size);
+    fInternal.setCountExact(fCapacity);
+    SkASSERT(fInternal.count() == (int)fCapacity);
+    // read back the capacity in case it was already larger than this
+    fCapacity = fInternal.reserved();
     fData = fInternal.begin();
     if (wasExternal) {
         // we were external, so copy in the data
         memcpy(fData, fExternal, fUsed);
     }
-    // Find out the size the buffer grew to, it may be more than we asked for.
-    fCapacity = fInternal.reserved();
-    // Expand the array so all reserved space is "used", we maintain the
-    // amount we have written manually outside the array
-    fInternal.setCount(fCapacity);
-    SkASSERT(fInternal.count() == (int)fCapacity);
     SkASSERT(fInternal.reserved() == (int)fCapacity);
 }