Switch deque to forward_list for memory use.

Landing this to test the difference in memory consumption vs deque. If
this doesn't help, we can try a different approach.

Change-Id: I7d0e8a2e694671db7e7627754bc305991fea5b5c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/399016
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

src/sksl/ir/SkSLSymbolTable.cpp

@@ -82,10 +82,9 @@ const Symbol* SymbolTable::lookup(SymbolTable* writableSymbolTable, const Symbol
 }
 
 const String* SymbolTable::takeOwnershipOfString(String str) {
-    fOwnedStrings.push_back(std::move(str));
-    // Because fOwnedStrings is a deque and we only push_back new elements onto it, and never erase
-    // or reorder, returning a pointer to an element here is safe.
-    return &fOwnedStrings.back();
+    fOwnedStrings.push_front(std::move(str));
+    // Because fOwnedStrings is a linked list, pointers to elements are stable.
+    return &fOwnedStrings.front();
 }
 
 void SymbolTable::addAlias(StringFragment name, const Symbol* symbol) {

src/sksl/ir/SkSLSymbolTable.h

@@ -14,7 +14,7 @@
 #include "include/private/SkTHash.h"
 #include "src/sksl/SkSLErrorReporter.h"
 
-#include <deque>
+#include <forward_list>
 #include <memory>
 #include <vector>
 
@@ -139,8 +139,7 @@ private:
 
     bool fBuiltin = false;
     std::vector<std::unique_ptr<IRNode>> fOwnedNodes;
-    // A deque is used here because insertion is guaranteed not to invalidate the pointers inside.
-    std::deque<String> fOwnedStrings;
+    std::forward_list<String> fOwnedStrings;
     SkTHashMap<SymbolKey, const Symbol*, SymbolKey::Hash> fSymbols;
     ErrorReporter& fErrorReporter;