bug 408124. increase size of regexp arena to avoid unnecessary additional allocations. r=crowder

js/src/jsregexp.c

@@ -3371,7 +3371,14 @@ js_ExecuteRegExp(JSContext *cx, JSRegExp *re, JSString *str, size_t *indexp,
     gData.start = start;
     gData.skipped = 0;
 
-    JS_INIT_ARENA_POOL(&gData.pool, "RegExpPool", 8096, 4,
+    /*
+     * To avoid multiple allocations in InitMatch(), the arena size parameter
+     * should be at least as big as:
+     * INITIAL_BACKTRACK
+     * + (sizeof(REProgState) * INITIAL_STATESTACK)
+     * + (offsetof(REMatchState, parens) + avgParanSize * sizeof(RECapture))
+     */
+    JS_INIT_ARENA_POOL(&gData.pool, "RegExpPool", 12288, 4,
                        &cx->scriptStackQuota);
     x = InitMatch(cx, &gData, re, length);