Bug 1510463 - Allow adding breakpoints without pausing. r=jlast

Differential Revision: https://phabricator.services.mozilla.com/D13737

--HG--
extra : moz-landing-system : lando

devtools/server/actors/root.js

@@ -136,6 +136,9 @@ RootActor.prototype = {
     noBlackBoxing: false,
     // Support for server pretty-printing has been removed.
     noPrettyPrinting: true,
+    // Added in Firefox 66. Indicates that clients do not need to pause the
+    // debuggee before adding breakpoints.
+    breakpointWhileRunning: true,
     // Trait added in Gecko 38, indicating that all features necessary for
     // grabbing allocations from the MemoryActor are available for the performance tool
     memoryActorAllocations: true,

devtools/shared/client/source-client.js

@@ -194,6 +194,12 @@ SourceClient.prototype = {
       });
     };
 
+    // With async sourcemap processing removed from the server, it is not
+    // necessary for clients to pause the debuggee before adding breakpoints.
+    if (this._client.mainRoot.traits.breakpointWhileRunning) {
+      return doSetBreakpoint();
+    }
+
     // If the debuggee is paused, just set the breakpoint.
     if (this._activeThread.paused) {
       return doSetBreakpoint();