SkPDF: cache metrics once.

include/private/SkTHash.h

Index: include/private/SkTHash.h
diff --git a/include/private/SkTHash.h b/include/private/SkTHash.h
index 8a644e3b019750a768c806934f9635925b3e0f6b..1e8602543dd0e1a5ea6dcf081126992376269053 100644
--- a/include/private/SkTHash.h
+++ b/include/private/SkTHash.h
@@ -48,15 +48,16 @@ public:
     // The pointers returned by set() and find() are valid only until the next call to set().
     // The pointers you receive in foreach() are only valid for its duration.
 
-    // Copy val into the hash table, returning a pointer to the copy now in the table.
+    // Move val into the hash table, returning a pointer to the copy now in the table.
     // If there already is an entry in the table with the same key, we overwrite it.
-    T* set(const T& val) {
+    T* set(T val) {
         if (4 * (fCount+fRemoved) >= 3 * fCapacity) {
             this->resize(fCapacity > 0 ? fCapacity * 2 : 4);
         }
-        return this->uncheckedSet(val);
+        return this->uncheckedSet(std::move(val));
     }
 
+
     // If there is an entry in the table with this key, return a pointer to it.  If not, NULL.
     T* find(const K& key) const {
         uint32_t hash = Hash(key);
@@ -116,7 +117,7 @@ public:
     }
 
 private:
-    T* uncheckedSet(const T& val) {
+    T* uncheckedSet(T val) {
         const K& key = Traits::GetKey(val);
         uint32_t hash = Hash(key);
         int index = hash & (fCapacity-1);
@@ -127,7 +128,7 @@ private:
                 if (s.removed()) {
                     fRemoved--;
                 }
-                s.val  = val;
+                s.val  = std::move(val);
                 s.hash = hash;
                 fCount++;
                 return &s.val;
@@ -135,7 +136,7 @@ private:
             if (hash == s.hash && key == Traits::GetKey(s.val)) {
                 // Overwrite previous entry.
                 // Note: this triggers extra copies when adding the same value repeatedly.
-                s.val = val;
+                s.val = std::move(val);
                 return &s.val;
             }
             index = this->next(index, n);
@@ -156,7 +157,7 @@ private:
         for (int i = 0; i < oldCapacity; i++) {
             const Slot& s = oldSlots[i];
             if (!s.empty() && !s.removed()) {
-                this->uncheckedSet(s.val);
+                this->uncheckedSet(std::move(s.val));
             }
         }
         SkASSERT(fCount == oldCount);
@@ -209,9 +210,8 @@ public:
 
     // Set key to val in the table, replacing any previous value with the same key.
     // We copy both key and val, and return a pointer to the value copy now in the table.
-    V* set(const K& key, const V& val) {
-        Pair in = { key, val };
-        Pair* out = fTable.set(in);
+    V* set(const K& key, V val) {
+        Pair* out = fTable.set(Pair{ key, std::move(val) });
         return &out->val;
     }