Document ART's `--verbose-methods` compiler option in dex2oat's usage.

Test: Run "dex2oat --help" and check the output
Change-Id: Ib496563379a11a1e6d036a80c7f862dd67673999
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index 278523e..e1a0e9a 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -437,6 +437,10 @@
   UsageError("      the default behavior). This option is only meaningful when used with");
   UsageError("      --dump-cfg.");
   UsageError("");
+  UsageError("  --verbose-methods=<method-names>: Restrict dumped CFG data to methods whose name");
+  UsageError("      contain one of the method names passed as argument");
+  UsageError("      Example: --verbose-methods=toString,hashCode");
+  UsageError("");
   UsageError("  --classpath-dir=<directory-path>: directory used to resolve relative class paths.");
   UsageError("");
   UsageError("  --class-loader-context=<string spec>: a string specifying the intended");