Add WebDragData to blink::WebView::dragtargetDrop

content/public/common/drop_data.h

Index: content/public/common/drop_data.h
diff --git a/content/public/common/drop_data.h b/content/public/common/drop_data.h
index fce6db13774f772181d135a12c452ff553f58699..923fb56c68f614a732a349f2f07b23b766653207 100644
--- a/content/public/common/drop_data.h
+++ b/content/public/common/drop_data.h
@@ -32,6 +32,27 @@ struct CONTENT_EXPORT DropData {
     int64_t size;
   };
 
+  enum class Kind {
+    STRING = 0,
+    FILENAME,
+    FILESYSTEMFILE,
+    LAST = FILESYSTEMFILE
+  };
+
+  struct MetaData {

[dcheng, 2016/05/24 05:51:50]

Nit: Metadata instead of MetaData, as that seems to be more prevalent

[hush (inactive), 2016/05/24 20:26:09]

Done.

+    MetaData();
+    MetaData(const DropData::Kind& kind, const base::string16& mime_type);

[dcheng, 2016/05/24 05:51:50]

Hmm. Rather than having constructors and having to pass the kind explicitly, I
suggest something like:

MetaData::CreateForMimeType(...)
MetaData::CreateForFilePath(...)
MetaData::CreateForFilesystemUrl(...)

[hush (inactive), 2016/05/24 20:26:09]

Sorry I don't see the benefit of these static factory methods.
The kind is implicit only for CreateForFilePath and CreateForFileSystemUrl.
CreateForMimeType still needs both mime type and kind, because kind could be
both string and filename. 
These static factory methods also make "DropDataToMeta" more verbose because we
have to use push_back instead of emplace_back. And we also incur more copies as
a result of using static factory methods (one in the factory method itself, one
in push_back)

How about keeping these 3 constructors, but only pass kind when the 2nd
parameter is mime type, because that's the only case where kind is unclear?

[dcheng, 2016/05/25 00:07:58]

The main reason I suggested factory functions is to help overall readability. If
I see:

Metadata(const GURL&);

it's hard to tell it's only for filesystem URLs and not for other kinds of URLs.

But if I have:

Metadata::CreateForFilesystemUrl(...)

Then it's unambiguous.

As for the extra copy... if it really matters, we should give it a move
constructor. Otherwise we shouldn't worry about it.

[hush (inactive), 2016/05/25 02:31:16]

OK. I did the static factory methods.

+    MetaData(const DropData::Kind& kind, const base::FilePath& filename);
+    MetaData(const DropData::Kind& kind, const GURL& file_system_url);
+    MetaData(const MetaData& other);
+    ~MetaData();
+
+    DropData::Kind kind;
+    base::string16 mime_type;
+    base::FilePath filename;
+    GURL file_system_url;
+  };
+
   DropData();
   DropData(const DropData& other);
   ~DropData();
@@ -54,6 +75,8 @@ struct CONTENT_EXPORT DropData {
   // populated if the drag is not renderer tainted, as this allows File access
   // from web content.
   std::vector<ui::FileInfo> filenames;
+  // The mime types of dragged files.
+  std::vector<base::string16> file_mime_types;
 
   // Isolated filesystem ID for the files being dragged on the webview.
   base::string16 filesystem_id;