mark request as cancelled immediately after verifier is cancelled

in case send errors prevent us from receiving remote echo

src/crypto/verification/Base.js

@@ -287,6 +287,7 @@ export class VerificationBase extends EventEmitter {
         this._endTimer(); // always kill the activity timer
         if (!this._done) {
             this.cancelled = true;
+            this.request.onVerifierCancelled();
             if (this.userId && this.deviceId) {
                 // send a cancellation to the other user (if it wasn't
                 // cancelled by the other user)

src/crypto/verification/request/VerificationRequest.js

@@ -73,6 +73,7 @@ export class VerificationRequest extends EventEmitter {
         this._accepting = false;
         this._declining = false;
         this._verifierHasFinished = false;
+        this._cancelled = false;
         this._chosenMethod = null;
         // we keep a copy of the QR Code data (including other user master key) around
         // for QR reciprocate verification, to protect against
@@ -525,7 +526,7 @@ export class VerificationRequest extends EventEmitter {
         }
 
         const cancelEvent = this._getEventByEither(CANCEL_TYPE);
-        if (cancelEvent && phase() !== PHASE_DONE) {
+        if ((this._cancelled || cancelEvent) && phase() !== PHASE_DONE) {
             transitions.push({phase: PHASE_CANCELLED, event: cancelEvent});
             return transitions;
         }
@@ -858,6 +859,15 @@ export class VerificationRequest extends EventEmitter {
         return true;
     }
 
+    onVerifierCancelled() {
+        this._cancelled = true;
+        // move to cancelled phase
+        const newTransitions = this._applyPhaseTransitions();
+        if (newTransitions.length) {
+            this._setPhase(newTransitions[newTransitions.length - 1].phase);
+        }
+    }
+
     onVerifierFinished() {
         this.channel.send("m.key.verification.done", {});
         this._verifierHasFinished = true;