Double allocation size for special json strings on every resize (fixes

crbug 83877)

The issue was that with the relatively small start and increment size of the string we created a ton of string handles when scanning a large string with special characters (500k+ in this case).

In addition, since we can not be sure the the newly allocated string
is in newspace a check is introduced and if not a filler object is
inserted instead of shrinking.
Review URL: http://codereview.chromium.org/7075009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8082 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/json-parser.cc

@@ -380,7 +380,7 @@ Token::Value JsonParser::SlowScanJsonString() {
   while (c0_ != '"') {
     // Create new seq string
     if (count >= kInitialSpecialStringSize * allocation_count) {
-      allocation_count++;
+      allocation_count = allocation_count * 2;
       int new_size = allocation_count * kInitialSpecialStringSize;
       Handle<String> new_two_byte =
           isolate()->factory()->NewRawTwoByteString(new_size,
@@ -443,10 +443,18 @@ Token::Value JsonParser::SlowScanJsonString() {
   Advance();
 
   // Shrink the the string to our length.
-  isolate()->heap()->
-      new_space()->
-      ShrinkStringAtAllocationBoundary<SeqTwoByteString>(*seq_two_byte,
-                                                         count);
+  if (isolate()->heap()->InNewSpace(*seq_two_byte)) {
+    isolate()->heap()->new_space()->
+          ShrinkStringAtAllocationBoundary<SeqTwoByteString>(*seq_two_byte,
+                                                             count);
+  } else {
+    int string_size = SeqTwoByteString::SizeFor(count);
+    int allocated_string_size =
+        SeqTwoByteString::SizeFor(kInitialSpecialStringSize * allocation_count);
+    int delta = allocated_string_size - string_size;
+    Address start_filler_object = seq_two_byte->address() + string_size;
+    isolate()->heap()->CreateFillerObjectAt(start_filler_object, delta);
+  }
   string_val_ = isolate()->factory()->NewConsString(ascii, seq_two_byte);
   return Token::STRING;
 }

src/json-parser.h

@@ -135,7 +135,7 @@ class JsonParser BASE_EMBEDDED {
     int end_pos;
   };
 
-  static const int kInitialSpecialStringSize = 100;
+  static const int kInitialSpecialStringSize = 1024;
 
 
  private: