Support column-based breakpoints in the VM and Observatory.

runtime/vm/debugger_api_impl.cc

Index: runtime/vm/debugger_api_impl.cc
diff --git a/runtime/vm/debugger_api_impl.cc b/runtime/vm/debugger_api_impl.cc
index 9fd26d88030e6cfb14ca3210fcacc358d39ab61c..ad0198b7eb601959baf11498976ad929fba853df 100644
--- a/runtime/vm/debugger_api_impl.cc
+++ b/runtime/vm/debugger_api_impl.cc
@@ -361,7 +361,11 @@ DART_EXPORT Dart_Handle Dart_GetBreakpointLine(intptr_t bp_id) {
     return Api::NewError("%s: breakpoint with id %" Pd " does not exist",
                          CURRENT_FUNC, bp_id);
   }
-  return Dart_NewInteger(bpt->bpt_location()->LineNumber());
+  if (bpt->bpt_location()->IsResolved()) {
+    return Dart_NewInteger(bpt->bpt_location()->LineNumber());
+  } else {
+    return Dart_NewInteger(bpt->bpt_location()->requested_line_number());
+  }
 }