feat: add support for Blob's going over the ctx bridge (#29247)

docs/api/context-bridge.md

@@ -107,6 +107,7 @@ has been included below for completeness:
 | `Function` | Complex | ✅ | ✅ | Prototype modifications are dropped.  Sending classes or constructors will not work. |
 | [Cloneable Types](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm) | Simple | ✅ | ✅ | See the linked document on cloneable types |
 | `Element` | Complex | ✅ | ✅ | Prototype modifications are dropped.  Sending custom elements will not work. |
+| `Blob` | Complex | ✅ | ✅ | N/A |
 | `Symbol` | N/A | ❌ | ❌ | Symbols cannot be copied across contexts so they are dropped |
 
 If the type you care about is not in the above table, it is probably not supported.

shell/renderer/api/electron_api_context_bridge.cc

@@ -24,6 +24,7 @@
 #include "shell/common/gin_helper/promise.h"
 #include "shell/common/node_includes.h"
 #include "shell/common/world_ids.h"
+#include "third_party/blink/public/web/web_blob.h"
 #include "third_party/blink/public/web/web_element.h"
 #include "third_party/blink/public/web/web_local_frame.h"
 
@@ -346,6 +347,14 @@ v8::MaybeLocal<v8::Value> PassValueToOtherContext(
         destination_context->Global(), destination_context->GetIsolate()));
   }
 
+  // Custom logic to "clone" Blob references
+  blink::WebBlob blob = blink::WebBlob::FromV8Value(value);
+  if (!blob.IsNull()) {
+    v8::Context::Scope destination_context_scope(destination_context);
+    return v8::MaybeLocal<v8::Value>(blob.ToV8Value(
+        destination_context->Global(), destination_context->GetIsolate()));
+  }
+
   // Proxy all objects
   if (IsPlainObject(value)) {
     auto object_value = value.As<v8::Object>();

spec-main/api-context-bridge-spec.ts

@@ -584,6 +584,33 @@ describe('contextBridge', () => {
         expect(result).to.deep.equal(['BODY', 'HTMLBodyElement', 'function']);
       });
 
+      it('should handle Blobs', async () => {
+        await makeBindingWindow(() => {
+          contextBridge.exposeInMainWorld('example', {
+            getBlob: () => new Blob(['ab', 'cd'])
+          });
+        });
+        const result = await callWithBindings(async (root: any) => {
+          return [await root.example.getBlob().text()];
+        });
+        expect(result).to.deep.equal(['abcd']);
+      });
+
+      it('should handle Blobs going backwards over the bridge', async () => {
+        await makeBindingWindow(() => {
+          contextBridge.exposeInMainWorld('example', {
+            getBlobText: async (fn: Function) => {
+              const blob = fn();
+              return [await blob.text()];
+            }
+          });
+        });
+        const result = await callWithBindings((root: any) => {
+          return root.example.getBlobText(() => new Blob(['12', '45']));
+        });
+        expect(result).to.deep.equal(['1245']);
+      });
+
       // Can only run tests which use the GCRunner in non-sandboxed environments
       if (!useSandbox) {
         it('should release the global hold on methods sent across contexts', async () => {
@@ -789,7 +816,8 @@ describe('contextBridge', () => {
             symbolKeyed: {
               [Symbol('foo')]: 123
             },
-            getBody: () => document.body
+            getBody: () => document.body,
+            getBlob: () => new Blob(['ab', 'cd'])
           });
         });
         const result = await callWithBindings(async (root: any) => {
@@ -862,7 +890,8 @@ describe('contextBridge', () => {
             [(await example.object.getPromise()).arr[3][0], String],
             [arg, Object],
             [arg.key, String],
-            [example.getBody(), HTMLBodyElement]
+            [example.getBody(), HTMLBodyElement],
+            [example.getBlob(), Blob]
           ];
           return {
             protoMatches: protoChecks.map(([a, Constructor]) => Object.getPrototypeOf(a) === Constructor.prototype)