[NaCl SDK] Add comments in the implementation code of GoogleDriveFs

PNaCl is on a path to deprecation, and GoogleDriveFs is compiled from PNaCl,
so comments are added to the implementation code to inform that GoogleDriveFs
is not going to be further developed.

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_nacl_sdk;master.tryserver.chromium.mac:mac_nacl_sdk;master.tryserver.chromium.win:win_nacl_sdk

Review-Url: https://codereview.chromium.org/2937083003
Cr-Commit-Position: refs/heads/master@{#480250}

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs.cc

@@ -10,6 +10,10 @@
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 GoogleDriveFs::GoogleDriveFs() {}
 
 Error GoogleDriveFs::Init(const FsInitArgs& args) {

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs.h

@@ -12,6 +12,10 @@
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 class GoogleDriveFs : public Filesystem {
  protected:
   GoogleDriveFs();

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs_node.cc

@@ -13,6 +13,10 @@
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 GoogleDriveFsNode::GoogleDriveFsNode(GoogleDriveFs* googledrivefs)
     : Node(googledrivefs) {}
 

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs_node.h

@@ -14,6 +14,10 @@
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 class GoogleDriveFsNode : public Node {
  public:
   GoogleDriveFsNode(GoogleDriveFs* googledrivefs);