Add a const overload to DownloadItem::GetExternalData().

BUG=78085
TEST=unit_tests


Review URL: http://codereview.chromium.org/9518008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@124678 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/download/download_item_impl.cc

@@ -1131,9 +1131,17 @@ void DownloadItemImpl::MockDownloadOpenForTesting() { open_enabled_ = false; }
 
 DownloadItem::ExternalData*
 DownloadItemImpl::GetExternalData(const void* key) {
-  if (!ContainsKey(external_data_map_, key))
-    return NULL;
-  return external_data_map_[key];
+  // The behavior of the const overload is identical with the exception of the
+  // constness of |this| and the return value.
+  return const_cast<DownloadItem::ExternalData*>(
+      static_cast<const DownloadItemImpl&>(*this).GetExternalData(key));
+}
+
+const DownloadItem::ExternalData*
+DownloadItemImpl::GetExternalData(const void* key) const {
+  std::map<const void*, ExternalData*>::const_iterator it =
+      external_data_map_.find(key);
+  return (it == external_data_map_.end()) ? NULL : it->second;
 }
 
 void DownloadItemImpl::SetExternalData(

content/browser/download/download_item_impl.h

@@ -209,6 +209,7 @@ class CONTENT_EXPORT DownloadItemImpl : public content::DownloadItem {
   virtual std::string DebugString(bool verbose) const OVERRIDE;
   virtual void MockDownloadOpenForTesting() OVERRIDE;
   virtual ExternalData* GetExternalData(const void* key) OVERRIDE;
+  virtual const ExternalData* GetExternalData(const void* key) const OVERRIDE;
   virtual void SetExternalData(const void* key, ExternalData* data) OVERRIDE;
 
  private:

content/browser/download/download_item_impl_unittest.cc

@@ -294,9 +294,11 @@ class TestExternalData : public DownloadItem::ExternalData {
 
 TEST_F(DownloadItemTest, ExternalData) {
   DownloadItem* item = CreateDownloadItem(DownloadItem::IN_PROGRESS);
+  const DownloadItem* const_item = item;
 
   // Shouldn't be anything there before set.
   EXPECT_EQ(NULL, item->GetExternalData(&external_data_test_string));
+  EXPECT_EQ(NULL, const_item->GetExternalData(&external_data_test_string));
 
   TestExternalData* test1(new TestExternalData());
   test1->value = 2;
@@ -308,6 +310,13 @@ TEST_F(DownloadItemTest, ExternalData) {
           item->GetExternalData(&external_data_test_string));
   EXPECT_EQ(test1, test_result);
 
+  // Ditto for const lookup.
+  const TestExternalData* test_const_result =
+      static_cast<const TestExternalData*>(
+          const_item->GetExternalData(&external_data_test_string));
+  EXPECT_EQ(static_cast<const TestExternalData*>(test1),
+            test_const_result);
+
   // Destructor should be called if value overwritten.  New value
   // should then be retrievable.
   TestExternalData* test2(new TestExternalData());

content/public/browser/download_item.h

@@ -344,7 +344,8 @@ class CONTENT_EXPORT DownloadItem {
   // If an object is already held by the DownloadItem associated with
   // the passed key, it will be destroyed if overwriten by a new pointer
   // (overwrites by the same pointer are ignored).
-  virtual ExternalData* GetExternalData(const void* key) = 0;
+  virtual       ExternalData* GetExternalData(const void* key) = 0;
+  virtual const ExternalData* GetExternalData(const void* key) const = 0;
   virtual void SetExternalData(const void* key, ExternalData* data) = 0;
 
   virtual std::string DebugString(bool verbose) const = 0;

content/test/mock_download_item.h

@@ -116,6 +116,7 @@ class MockDownloadItem : public content::DownloadItem {
   MOCK_CONST_METHOD1(DebugString, std::string(bool));
   MOCK_METHOD0(MockDownloadOpenForTesting, void());
   MOCK_METHOD1(GetExternalData, ExternalData*(const void*));
+  MOCK_CONST_METHOD1(GetExternalData, const ExternalData*(const void*));
   MOCK_METHOD2(SetExternalData, void(const void*, ExternalData*));
 };