fix(focus-trap): wrong element being checked when logging deprecation warning

Fixes the host element being checked when logging out the deprecation warning, rather than the deprecated element itself. Also adds deletion targets so we don't miss to deprecate the selectors in 7.0.0.

Fixes #10566.

Author: crisbeto

src/cdk/a11y/focus-trap/focus-trap.ts

@@ -146,12 +146,15 @@ export class FocusTrap {
                                                  `[cdk-focus-${bound}]`) as NodeListOf<HTMLElement>;
 
     for (let i = 0; i < markers.length; i++) {
+      // @deletion-target 7.0.0
       if (markers[i].hasAttribute(`cdk-focus-${bound}`)) {
-        console.warn(`Found use of deprecated attribute 'cdk-focus-${bound}',` +
-                     ` use 'cdkFocusRegion${bound}' instead.`, markers[i]);
+        console.warn(`Found use of deprecated attribute 'cdk-focus-${bound}', ` +
+                     `use 'cdkFocusRegion${bound}' instead. The deprecated ` +
+                     `attribute will be removed in 7.0.0.`, markers[i]);
       } else if (markers[i].hasAttribute(`cdk-focus-region-${bound}`)) {
-        console.warn(`Found use of deprecated attribute 'cdk-focus-region-${bound}',` +
-                     ` use 'cdkFocusRegion${bound}' instead.`, markers[i]);
+        console.warn(`Found use of deprecated attribute 'cdk-focus-region-${bound}', ` +
+                     `use 'cdkFocusRegion${bound}' instead. The deprecated attribute ` +
+                     `will be removed in 7.0.0.`, markers[i]);
       }
     }
 
@@ -171,9 +174,11 @@ export class FocusTrap {
     const redirectToElement = this._element.querySelector(`[cdk-focus-initial], ` +
                                                           `[cdkFocusInitial]`) as HTMLElement;
 
-    if (this._element.hasAttribute(`cdk-focus-initial`)) {
-      console.warn(`Found use of deprecated attribute 'cdk-focus-initial',` +
-                    ` use 'cdkFocusInitial' instead.`, this._element);
+    // @deletion-target 7.0.0
+    if (redirectToElement.hasAttribute(`cdk-focus-initial`)) {
+      console.warn(`Found use of deprecated attribute 'cdk-focus-initial', ` +
+                   `use 'cdkFocusInitial' instead. The deprecated attribute ` +
+                   `will be removed 7.0.0`, redirectToElement);
     }
 
     if (redirectToElement) {