Add adbconnection plugin

This plugin will take care of creating and managing a debugger connection
through the adb daemon. This involves sending DDMS messages from the
runtime, loading the JDWP agent when required, and setting up the
connection. We need this since DDMS packets can be sent even if there has
not been a full handshake done with the JDWP agent.

Add an 'adbconnection' value to '-XjdwpProvider:...' to allow one to
request that the adbconnection plugin be used to provide JDWP
functionality.

Bug: 62821960
Test: Manual, Flash walleye, debug apps

Change-Id: Id9bed589b7c5e3830e6cdfbfee460b091459a27b
diff --git a/cmdline/cmdline_types.h b/cmdline/cmdline_types.h
index 5c887f8..529fe2b 100644
--- a/cmdline/cmdline_types.h
+++ b/cmdline/cmdline_types.h
@@ -75,10 +75,13 @@
       return Result::Usage(
           "Example: -XjdwpProvider:none to disable JDWP\n"
           "Example: -XjdwpProvider:internal for internal jdwp implementation\n"
+          "Example: -XjdwpProvider:adbconnection for adb connection mediated jdwp implementation\n"
           "Example: -XjdwpProvider:default for the default jdwp implementation"
           " (currently internal)\n");
     } else if (option == "internal" || option == "default") {
       return Result::Success(JdwpProvider::kInternal);
+    } else if (option == "adbconnection") {
+      return Result::Success(JdwpProvider::kAdbConnection);
     } else if (option == "none") {
       return Result::Success(JdwpProvider::kNone);
     } else {