[PPAPI] It is now possible to pass a FileSystem to JS in PostMessage.

content/renderer/pepper/resource_converter.cc

Index: content/renderer/pepper/resource_converter.cc
diff --git a/content/renderer/pepper/resource_converter.cc b/content/renderer/pepper/resource_converter.cc
index 5b564f125de9dc7ec85c7e0ac62ea143c755b6c7..3118af669f2e05a7d288034c897e059f45de0b94 100644
--- a/content/renderer/pepper/resource_converter.cc
+++ b/content/renderer/pepper/resource_converter.cc
@@ -20,6 +20,11 @@
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 #include "third_party/WebKit/public/web/WebDOMFileSystem.h"
 #include "third_party/WebKit/public/web/WebDOMMediaStreamTrack.h"
+#include "third_party/WebKit/public/web/WebFrame.h"
+// TODO(mgiuca): This include is not allowed from content/renderer. This is
+// needed to parse a file system URL. Perhaps it can be moved to webkit/common?
+#include "webkit/browser/fileapi/file_system_url.h"
+#include "webkit/common/fileapi/file_system_util.h"
 
 using ppapi::ResourceVar;
 
@@ -54,6 +59,29 @@ PP_FileSystemType WebFileSystemTypeToPPAPI(blink::WebFileSystem::Type type) {
   }
 }
 
+// Converts a fileapi::FileSystemType to a blink::WebFileSystemType.
+// Returns true on success, false on failure.
+bool FileApiFileSystemTypeToWebFileSystemType(
+    fileapi::FileSystemType type,
+    blink::WebFileSystemType* result_type) {
+  switch (type) {
+    case fileapi::kFileSystemTypeTemporary:
+      *result_type = blink::WebFileSystemTypeTemporary;
+      return true;
+    case fileapi::kFileSystemTypePersistent:
+      *result_type = blink::WebFileSystemTypePersistent;
+      return true;
+    case fileapi::kFileSystemTypeIsolated:
+      *result_type = blink::WebFileSystemTypeIsolated;
+      return true;
+    case fileapi::kFileSystemTypeExternal:
+      *result_type = blink::WebFileSystemTypeExternal;

[kinuko, 2014/02/20 11:33:28]

As you can see in file_system_types.h, these are guaranteed to be the same value
so that just static_cast should work.  (If you want extra guarantee you can add
static assertion)

[Matt Giuca, 2014/02/23 23:55:48]

I'm uncomfortable relying on that fact. Besides, I'm converting from
FileSystemType (which is a superset of WebFileSystemType), not the other way
around. We need a switch to ensure that it is one of these four types, and if
not, it needs to be an error.

(Note: I wasn't checking this error before, now I am.)

For example, apparently ParseFileSystemSchemeURL will return a mount_type of
kFileSystemTypeTest if it encounters a path starting with "/test". This should
be an error because it is not convertible to a blink::WebFileSystemType.

+      return true;
+    default:
+      return false;
+  }
+}
+
 // Given a V8 value containing a DOMFileSystem, creates a resource host and
 // returns the resource information for serialization.
 // On error, false.
@@ -92,6 +120,26 @@ bool DOMFileSystemToResource(
   return true;
 }
 
+v8::Handle<v8::Value> ResourceHostToDOMFileSystem(
+    content::PepperFileSystemHost* file_system_host,
+    v8::Handle<v8::Context> context) {
+  GURL root_url = file_system_host->GetRootUrl();
+  GURL origin;
+  fileapi::FileSystemType mount_type;
+  base::FilePath virtual_path;
+  fileapi::FileSystemURL::ParseFileSystemSchemeURL(
+      root_url, &origin, &mount_type, &virtual_path);
+
+  std::string name = GetFileSystemName(origin, mount_type);
+  blink::WebFileSystemType blink_type;
+  FileApiFileSystemTypeToWebFileSystemType(mount_type, &blink_type);
+  blink::WebFrame* frame = blink::WebFrame::frameForContext(context);
+  return frame->createSerializableFileSystem(
+      blink_type,
+      blink::WebString::fromUTF8(name),
+      blink::WebString::fromUTF8(root_url.spec()));
+}
+
 bool DOMMediaStreamTrackToResource(
     PP_Instance instance,
     RendererPpapiHost* host,
@@ -233,11 +281,15 @@ bool ResourceConverterImpl::ToV8Value(const PP_Var& var,
   }
 
   // Convert to the appropriate type of resource host.
-  // TODO(mgiuca): Convert FileSystemHost resources into DOMFileSystem V8
-  // objects. (http://crbug.com/345158)
-  LOG(ERROR) << "The type of resource #" << resource_id
-             << " cannot be converted to a JavaScript object.";
-  return false;
+  if (resource_host->IsFileSystemHost()) {
+    *result = ResourceHostToDOMFileSystem(
+        static_cast<content::PepperFileSystemHost*>(resource_host), context);
+    return true;
+  } else {
+    LOG(ERROR) << "The type of resource #" << resource_id
+               << " cannot be converted to a JavaScript object.";
+    return false;
+  }
 }
 
 scoped_refptr<HostResourceVar> ResourceConverterImpl::CreateResourceVar(