Enable strict-virtual-specifiers for iOS builds.

components/enhanced_bookmarks/image_store_util_ios.mm

Index: components/enhanced_bookmarks/image_store_util_ios.mm
diff --git a/components/enhanced_bookmarks/image_store_util_ios.mm b/components/enhanced_bookmarks/image_store_util_ios.mm
index 8e6b53f3afbcdbf539918b90b3268b6b4b6a0ef7..5d027cbaaaef195aba1b8abe53ee07ef8a81e83b 100644
--- a/components/enhanced_bookmarks/image_store_util_ios.mm
+++ b/components/enhanced_bookmarks/image_store_util_ios.mm
@@ -16,16 +16,14 @@ class RefCountedNSDataMemory : public base::RefCountedMemory {
  public:
   explicit RefCountedNSDataMemory(NSData* memory) : data_([memory retain]) {}
 
-  virtual const unsigned char* front() const override {
+  const unsigned char* front() const override {
     return reinterpret_cast<const unsigned char*>([data_ bytes]);
   }
 
-  virtual size_t size() const override {
-    return [data_ length];
-  }
+  size_t size() const override { return [data_ length]; }
 
 private:
-  virtual ~RefCountedNSDataMemory() {}
+ ~RefCountedNSDataMemory() override {}
 
   base::scoped_nsobject<NSData> data_;
   DISALLOW_COPY_AND_ASSIGN(RefCountedNSDataMemory);