Bug 1913520 - Make filled fields data for FormAutofill use Map instead of Object. r=credential-management-reviewers,dimi

My main motivation is that it is easier to type Maps than Objects-as-maps, but
using Objects as maps can have some odd behavior if you aren't careful, so I
think it is probably a better idea to use anyways for this data that might
be coming from a compromised child process.

This slightly alters the behavior of autofillFields because it modifies
the existing map in place rather than creating a new one from scratch,
but I think that is preferable because nothing seems to have an external
reference so there's no need to preserve the old map.

Differential Revision: https://phabricator.services.mozilla.com/D219361

browser/extensions/formautofill/test/browser/head.js

@@ -886,7 +886,7 @@ function verifySectionAutofillResult(section, result, expectedSection) {
   fieldDetails.forEach((field, fieldIndex) => {
     const expected = expectedFieldDetails[fieldIndex];
     Assert.equal(
-      result[field.elementId].value,
+      result.get(field.elementId).value,
       expected.autofill ?? "",
       `Autofilled value for element(identifier:${field.identifier}, field name:${field.fieldName}) should be equal`
     );

toolkit/components/formautofill/FormAutofillChild.sys.mjs

@@ -435,7 +435,7 @@ export class FormAutofillChild extends JSWindowActorChild {
   }
 
   async fillFields(focusedElementId, elementIds, profile) {
-    let result = {};
+    let result = new Map();
     try {
       Services.obs.notifyObservers(null, "autofill-fill-starting");
       const handler = this.#getHandlerByElementId(elementIds[0]);

toolkit/components/formautofill/FormAutofillParent.sys.mjs

@@ -822,7 +822,7 @@ export class FormAutofillParent extends JSWindowActorParent {
 
     const ids = section.fieldDetails.map(detail => detail.elementId);
 
-    let filledResult = {};
+    let filledResult = new Map();
     try {
       filledResult = await this.sendQuery("FormAutofill:FillFields", {
         focusedElementId: elementId,
@@ -830,10 +830,8 @@ export class FormAutofillParent extends JSWindowActorParent {
         profile,
       });
 
-      this.filledResult = {
-        ...(this.filledResult ?? {}),
-        ...filledResult,
-      };
+      this.filledResult = this.filledResult ?? new Map();
+      filledResult.forEach((value, key) => this.filledResult.set(key, value));
 
       section.onFilled(filledResult);
     } catch (e) {
@@ -845,11 +843,11 @@ export class FormAutofillParent extends JSWindowActorParent {
   }
 
   onFieldFilledModified(elementId) {
-    if (!this.filledResult?.[elementId]) {
+    if (!this.filledResult?.get(elementId)) {
       return;
     }
 
-    this.filledResult[elementId].filledState = FIELD_STATES.NORMAL;
+    this.filledResult.get(elementId).filledState = FIELD_STATES.NORMAL;
 
     const section = this.getSectionByElementId(elementId);
 
@@ -865,7 +863,7 @@ export class FormAutofillParent extends JSWindowActorParent {
       if (
         inputs.every(
           field =>
-            this.filledResult[field.elementId].filledState ==
+            this.filledResult.get(field.elementId).filledState ==
             FIELD_STATES.NORMAL
         )
       ) {

toolkit/components/formautofill/shared/AutofillTelemetry.sys.mjs

@@ -122,7 +122,7 @@ class AutofillTelemetryBase {
     const extra = this.#initFormEventExtra("unavailable");
 
     for (const fieldDetail of fieldDetails) {
-      let { filledState, value } = data[fieldDetail.elementId];
+      let { filledState, value } = data.get(fieldDetail.elementId);
       switch (filledState) {
         case FIELD_STATES.AUTO_FILLED:
           filledState = "filled";
@@ -152,7 +152,7 @@ class AutofillTelemetryBase {
     const extra = this.#initFormEventExtra("unavailable");
 
     for (const fieldDetail of fieldDetails) {
-      let { filledState, value } = data[fieldDetail.elementId];
+      let { filledState, value } = data.get(fieldDetail.elementId);
       switch (filledState) {
         case FIELD_STATES.AUTO_FILLED:
           filledState = "autofilled";

toolkit/components/formautofill/shared/FormAutofillHandler.sys.mjs

@@ -945,15 +945,15 @@ export class FormAutofillHandler {
    * value: The value of the element
    */
   collectFormFilledData() {
-    const filledData = {};
+    const filledData = new Map();
 
     for (const fieldDetail of this.fieldDetails) {
       const element = fieldDetail.element;
-      filledData[fieldDetail.elementId] = {
+      filledData.set(fieldDetail.elementId, {
         filledState: element.autofillState,
         filledValue: this.computeFillingValue(fieldDetail),
         value: element.value,
-      };
+      });
     }
     return filledData;
   }

toolkit/components/formautofill/shared/FormAutofillSection.sys.mjs

@@ -294,7 +294,7 @@ export class FormAutofillSection {
     };
 
     for (const detail of this.fieldDetails) {
-      const { filledValue } = formFilledData[detail.elementId];
+      const { filledValue } = formFilledData.get(detail.elementId);
 
       if (
         !filledValue ||