aapt2: add 'dump overlayable' command

Add a command to print a resource table's <overlayable> resources. Given
the following input

  <overlayable name="TestResources">
    <policy type="system">
      <item type="string" name="a" />
    </policy>
    <policy type="sytem|vendor">
      <item type="string" name="b" />
      <item type="string" name="c" />
    </policy>
  </overlayable>

aapt2 dump overlayable will produce

  name="TestResources" actor=""
    policies="system"
      string/a
    policies="system|vendor"
      string/b
      string/c

Bug: 120609160
Test: manual (aapt2 dump overlayable $(gettop)/frameworks/base/cmds/idmap2/tests/data/target/target.apk)
Change-Id: I21041e6169c62d01f1a469624911ce7cad3e18a8
diff --git a/tools/aapt2/cmd/Dump.h b/tools/aapt2/cmd/Dump.h
index 7ded9bc..cd51f7a 100644
--- a/tools/aapt2/cmd/Dump.h
+++ b/tools/aapt2/cmd/Dump.h
@@ -240,6 +240,16 @@
   std::vector<std::string> files_;
 };
 
+class DumpOverlayableCommand : public DumpApkCommand {
+ public:
+  explicit DumpOverlayableCommand(text::Printer* printer, IDiagnostics* diag)
+      : DumpApkCommand("overlayable", printer, diag) {
+    SetDescription("Print the <overlayable> resources of an APK.");
+  }
+
+  int Dump(LoadedApk* apk) override;
+};
+
 /** The default dump command. Performs no action because a subcommand is required. */
 class DumpCommand : public Command {
  public:
@@ -255,8 +265,8 @@
     AddOptionalSubcommand(util::make_unique<DumpTableCommand>(printer, diag_));
     AddOptionalSubcommand(util::make_unique<DumpXmlStringsCommand>(printer, diag_));
     AddOptionalSubcommand(util::make_unique<DumpXmlTreeCommand>(printer, diag_));
+    AddOptionalSubcommand(util::make_unique<DumpOverlayableCommand>(printer, diag_));
     AddOptionalSubcommand(util::make_unique<DumpBadgerCommand>(printer), /* hidden */ true);
-    // TODO(b/120609160): Add aapt2 overlayable dump command
   }
 
   int Action(const std::vector<std::string>& args) override {