[SystemInfo API] Implement storage.getAvailableCapacity API

chrome/common/extensions/api/system_storage.idl

Index: chrome/common/extensions/api/system_storage.idl
diff --git a/chrome/common/extensions/api/system_storage.idl b/chrome/common/extensions/api/system_storage.idl
index 33338d4a1ed40c70fccbe0a154fa54b671974b14..04fdd6be51033ecc59a8ea7e5a5795f97230fe6d 100644
--- a/chrome/common/extensions/api/system_storage.idl
+++ b/chrome/common/extensions/api/system_storage.idl
@@ -30,6 +30,12 @@ namespace system.storage {
     double capacity;
   };
 
+  dictionary StorageAvailableCapacityInfo {
+    DOMString id;

[Greg Billock, 2013/10/14 20:32:05]

Can we arrange to pass this in JS and just return the capacity in the callback?

[Haojian Wu, 2013/10/15 00:50:26]

Yes. We can just return the capacity instead of this structure.

But we have discussed with Hongbo in
CL:https://codereview.chromium.org/19053003/(see comments)

I think returning the capacity with corresponding storage device |id| in
callback function is better. Without the |id| field, developers should do extra
work to remember which storage device |id| does the |availableCapcity| belong
to, right?

[Greg Billock, 2013/10/15 15:26:04]

Sounds good.

On 2013/10/15 00:50:26, Haojian Wu wrote:

[Greg Billock, 2013/10/15 15:26:04]

Add a comment about this id that it is the same ID from StorageUnitInfo.

[Haojian Wu, 2013/10/16 04:04:23]

Done.

+    // The available capacity of the storage device, in bytes.
+    double availableCapacity;
+  };
+
   [inline_doc] enum EjectDeviceResultCode {
     // The ejection command is successful -- the application can prompt the user
     // to remove the device.
@@ -48,6 +54,9 @@ namespace system.storage {
 
   callback StorageInfoCallback = void (StorageUnitInfo[] info);
 
+  callback getAvailableCapacityCallback = void (
+      StorageAvailableCapacityInfo info);
+
   interface Functions {
     // Get the storage information from the system. The argument passed to the
     // callback is an array of StorageUnitInfo objects.
@@ -55,6 +64,10 @@ namespace system.storage {
 
     // Ejects a removable storage device.
     static void ejectDevice(DOMString id, EjectDeviceCallback callback);
+
+    // Get the available capacity of a specified |id| storage device.

[Greg Billock, 2013/10/15 15:26:04]

Clarify here about id: "... of a specified storage device. The |id| is the
transient device ID from StorageUnitInfo."

[Haojian Wu, 2013/10/16 04:04:23]

Done.

+    static void getAvailableCapacity(DOMString id,
+                                     getAvailableCapacityCallback callback);
   };
 
   interface Events {
@@ -66,4 +79,3 @@ namespace system.storage {
   };
 
 };
-