introduce a permission without sub-permissions in mediaGalleries API

We use mediaGalleries.getMetadata API to fetch media metadata in our Files.app(Chrome OS FileManager).

We pass the blob object(~binary data) to the API,
so we don't need any permissions.

This API has "read" permission, but this permission means "reading files in the MediaGallery", but we don't read it - the blob objects we pass is from filesystem, not from MediaGallery.

We need "empty" permissions, but if we pass a empty list as permissions, it causes permission error and the app doesn't start at all.

In this patch, I introduce a permission without sub-permissions,
and you can specify this permission in a manifest file like:

> "mediaGalleries",

https://developer.chrome.com/apps/mediaGalleries
BUG=581614

Review URL: https://codereview.chromium.org/1643183002

Cr-Commit-Position: refs/heads/master@{#375400}

6 files changed, 52 insertions, 2 deletions

diff --git a/extensions/common/permissions/media_galleries_permission.h b/extensions/common/permissions/media_galleries_permission.h
index 870a0a9..40a2277 100644
--- a/extensions/common/permissions/media_galleries_permission.h
+++ b/extensions/common/permissions/media_galleries_permission.h
@@ -21,6 +21,10 @@ namespace extensions {
 //                'delete' <tertiary-access>
 //   <tertiary-access>
 //             := 'copyTo' | 'copyTo' <tertiary-access>
+// An example of a line for mediaGalleries permissions in a manifest file:
+//   {"mediaGalleries": "read delete"},
+// We also allow a permission without any sub-permissions:
+//   "mediaGalleries",
 class MediaGalleriesPermission
   : public SetDisjunctionPermission<MediaGalleriesPermissionData,
                                     MediaGalleriesPermission> {
diff --git a/extensions/common/permissions/set_disjunction_permission.h b/extensions/common/permissions/set_disjunction_permission.h
index 0e97e9d..ce1c6ee 100644
--- a/extensions/common/permissions/set_disjunction_permission.h
+++ b/extensions/common/permissions/set_disjunction_permission.h
@@ -105,9 +105,14 @@ class SetDisjunctionPermission : public APIPermission {
     data_set_.clear();
     const base::ListValue* list = NULL;
 
-    if (!value || !value->GetAsList(&list) || list->GetSize() == 0) {
+    if (!value) {
+      // treat null as an empty list.
+      return true;
+    }
+
+    if (!value->GetAsList(&list)) {
       if (error)
-        *error = "NULL or empty permission list";
+        *error = "Cannot parse the permission list. It's not a list.";
       return false;
     }
 
diff --git a/extensions/common/permissions/socket_permission.cc b/extensions/common/permissions/socket_permission.cc
index c2ca223..a8e5c18 100644
--- a/extensions/common/permissions/socket_permission.cc
+++ b/extensions/common/permissions/socket_permission.cc
@@ -38,6 +38,21 @@ SocketPermission::SocketPermission(const APIPermissionInfo* info)
 
 SocketPermission::~SocketPermission() {}
 
+bool SocketPermission::FromValue(
+    const base::Value* value,
+    std::string* error,
+    std::vector<std::string>* unhandled_permissions) {
+  bool parsed_ok = SetDisjunctionPermission<
+      SocketPermissionData, SocketPermission>::FromValue(value, error,
+                                                         unhandled_permissions);
+  if (parsed_ok && data_set_.empty()) {
+    if (error)
+      *error = "NULL or empty permission list";
+    return false;
+  }
+  return parsed_ok;
+}
+
 PermissionIDSet SocketPermission::GetPermissions() const {
   PermissionIDSet ids;
   SocketPermissionEntrySet entries = ExtractSocketEntries(data_set_);
diff --git a/extensions/common/permissions/socket_permission.h b/extensions/common/permissions/socket_permission.h
index 01be06c..590ed5d 100644
--- a/extensions/common/permissions/socket_permission.h
+++ b/extensions/common/permissions/socket_permission.h
@@ -30,6 +30,12 @@ class SocketPermission
 
   ~SocketPermission() override;
 
+  // SetDisjunctionPermission overrides.
+  bool FromValue(const base::Value* value,
+                 std::string* error,
+                 std::vector<std::string>* unhandled_permissions) override;
+
+  // APIPermission overrides
   PermissionIDSet GetPermissions() const override;
 };
 
diff --git a/extensions/common/permissions/usb_device_permission.cc b/extensions/common/permissions/usb_device_permission.cc
index ab279b6..fd94783 100644
--- a/extensions/common/permissions/usb_device_permission.cc
+++ b/extensions/common/permissions/usb_device_permission.cc
@@ -25,6 +25,21 @@ UsbDevicePermission::UsbDevicePermission(const APIPermissionInfo* info)
 
 UsbDevicePermission::~UsbDevicePermission() {}
 
+bool UsbDevicePermission::FromValue(
+    const base::Value* value,
+    std::string* error,
+    std::vector<std::string>* unhandled_permissions) {
+  bool parsed_ok =
+      SetDisjunctionPermission<UsbDevicePermissionData, UsbDevicePermission>::
+          FromValue(value, error, unhandled_permissions);
+  if (parsed_ok && data_set_.empty()) {
+    if (error)
+      *error = "NULL or empty permission list";
+    return false;
+  }
+  return parsed_ok;
+}
+
 PermissionIDSet UsbDevicePermission::GetPermissions() const {
   PermissionIDSet ids;
 
diff --git a/extensions/common/permissions/usb_device_permission.h b/extensions/common/permissions/usb_device_permission.h
index 7cba580..2658011 100644
--- a/extensions/common/permissions/usb_device_permission.h
+++ b/extensions/common/permissions/usb_device_permission.h
@@ -30,6 +30,11 @@ class UsbDevicePermission
   explicit UsbDevicePermission(const APIPermissionInfo* info);
   ~UsbDevicePermission() override;
 
+  // SetDisjunctionPermission overrides.
+  bool FromValue(const base::Value* value,
+                 std::string* error,
+                 std::vector<std::string>* unhandled_permissions) override;
+
   // APIPermission overrides
   PermissionIDSet GetPermissions() const override;
 };