[IMP] web_editor: introduce a tool method to compute size of data URL

This commit extracts the calculation of the number of bytes within a
base64 data URL to a method named `getDataURLBinarySize`.

task-2835144

Part-of: odoo/odoo#103398

addons/web_editor/static/src/js/editor/image_processing.js

@@ -496,6 +496,15 @@ function createDataURL(blob) {
     });
 }
 
+/**
+ * @param {String} dataURL
+ * @returns {Number} number of bytes represented with base64
+ */
+function getDataURLBinarySize(dataURL) {
+    // Every 4 bytes of base64 represent 3 bytes.
+    return dataURL.split(',')[1].length / 4 * 3;
+}
+
 export default {
     applyModifications,
     cropperDataFields,
@@ -507,4 +516,5 @@ export default {
     isImageSupportedForStyle,
     createDataURL,
     isGif,
+    getDataURLBinarySize,
 };

addons/web_editor/static/src/js/editor/snippets.options.js

@@ -31,6 +31,7 @@ import {
     isImageSupportedForStyle,
     createDataURL,
     isGif,
+    getDataURLBinarySize,
 } from "web_editor.image_processing";
 import * as OdooEditorLib from "@web_editor/js/editor/odoo-editor/src/OdooEditor";
 import {SIZES, MEDIAS_BREAKPOINTS} from "@web/core/ui/ui_service";
@@ -5874,7 +5875,7 @@ const ImageHandlerOption = SnippetOptionWidget.extend({
             return;
         }
         const dataURL = await applyModifications(img, {mimetype: this._getImageMimetype(img)});
-        this._filesize = dataURL.split(',')[1].length / 4 * 3 / 1024;
+        this._filesize = getDataURLBinarySize(dataURL) / 1024;
 
         if (update) {
             img.classList.add('o_modified_image_to_save');