SQLite's recover.c should be valid C code

Move two variable declarations to the top of their function, so
Chromium's version of SQLite compiles on Windows. SQLite is used
by NSS on Dart's standalone Windows executable.

NOTRY=true
This is not based on src/, and is not tested until DEPS are updated.

This patch is not added to recover.patch, because the last 3 patches,
including the one this fixes, are not there, and recover.patch says:
    Since recover.c is in somewhat active development, it is possible that
    the patch below will not reliably re-create the file.

Review URL: https://codereview.chromium.org/552673003

Cr-Commit-Position: refs/heads/master@{#295260}

third_party/sqlite/amalgamation/sqlite3.c

@@ -110889,6 +110889,8 @@ static void interiorCursorDestroy(RecoverInteriorCursor *pCursor){
 /* Internal helper.  Reset storage in preparation for iterating pPage. */
 static void interiorCursorSetPage(RecoverInteriorCursor *pCursor,
                                   DbPage *pPage){
+  const unsigned knMinCellLength = 2 + 4 + 1;
+  unsigned nMaxChildren;
   assert( PageHeader(pPage)[kiPageTypeOffset]==kTableInteriorPage );
 
   if( pCursor->pPage ){
@@ -110909,8 +110911,7 @@ static void interiorCursorSetPage(RecoverInteriorCursor *pCursor,
    * each child contains a 32-bit page number and at least a varint (min size of
    * one byte).  The final child page is in the header.
    */
-  const unsigned knMinCellLength = 2 + 4 + 1;
-  unsigned nMaxChildren =
+  nMaxChildren =
       (pCursor->nPageSize - kiPageInteriorHeaderBytes) / knMinCellLength + 1;
   if (pCursor->nChildren > nMaxChildren) {
     pCursor->nChildren = nMaxChildren;

third_party/sqlite/src/src/recover.c

@@ -643,6 +643,8 @@ static void interiorCursorDestroy(RecoverInteriorCursor *pCursor){
 /* Internal helper.  Reset storage in preparation for iterating pPage. */
 static void interiorCursorSetPage(RecoverInteriorCursor *pCursor,
                                   DbPage *pPage){
+  const unsigned knMinCellLength = 2 + 4 + 1;
+  unsigned nMaxChildren;
   assert( PageHeader(pPage)[kiPageTypeOffset]==kTableInteriorPage );
 
   if( pCursor->pPage ){
@@ -669,8 +671,7 @@ static void interiorCursorSetPage(RecoverInteriorCursor *pCursor,
    * byte is corrupted.  Could be an overflow page, but it would require
    * a very large database.
    */
-  const unsigned knMinCellLength = 2 + 4 + 1;
-  unsigned nMaxChildren =
+  nMaxChildren =
       (pCursor->nPageSize - kiPageInteriorHeaderBytes) / knMinCellLength + 1;
   if (pCursor->nChildren > nMaxChildren) {
     pCursor->nChildren = nMaxChildren;