[psaux] Use doubling allocation strategy for CF2_ArrStack.

Fixes timeout reported as

  https://crbug.com/1206181

* src/psaux/psarrst.c (cf2_arrstack_{push,init}): Implement it.
* src/psaux/psarrst.h (CF2_ArrStackiRec): Drop `chunk'.

ChangeLog

@@ -1,3 +1,14 @@
+2021-05-13  Daniel McArdle  <dmcardle@chromium.org>
+
+	[psaux] Use doubling allocation strategy for CF2_ArrStack.
+
+	Fixes timeout reported as
+
+	  https://crbug.com/1206181
+
+	* src/psaux/psarrst.c (cf2_arrstack_{push,init}): Implement it.
+	* src/psaux/psarrst.h (CF2_ArrStackiRec): Drop `chunk'.
+
 2021-05-12  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	* src/smooth/ftgrays.c (FT_MAX_GRAY_SPANS): Increase from 10 to 16.

src/psaux/psarrst.c

@@ -65,7 +65,6 @@
     arrstack->error     = error;
     arrstack->sizeItem  = sizeItem;
     arrstack->allocated = 0;
-    arrstack->chunk     = 10;    /* chunks of 10 items */
     arrstack->count     = 0;
     arrstack->totalSize = 0;
     arrstack->ptr       = NULL;
@@ -216,9 +215,9 @@
 
     if ( arrstack->count == arrstack->allocated )
     {
-      /* grow the buffer by one chunk */
+      /* increase the buffer size */
       if ( !cf2_arrstack_setNumElements(
-             arrstack, arrstack->allocated + arrstack->chunk ) )
+             arrstack, arrstack->allocated * 2 + 16 ) )
       {
         /* on error, ignore the push */
         return;

src/psaux/psarrst.h

@@ -55,7 +55,6 @@ FT_BEGIN_HEADER
 
     size_t  sizeItem;       /* bytes per element             */
     size_t  allocated;      /* items allocated               */
-    size_t  chunk;          /* allocation increment in items */
     size_t  count;          /* number of elements allocated  */
     size_t  totalSize;      /* total bytes allocated         */