Rendering a web page using content communicated to a browser application from a process running on a client

1. A computer implemented method comprising:

receiving, by an Internet browser application executing on a client device, a markup language document from a web application associated with an online system, the web application configured to upload image files from the client device to a web server of the online system and the markup language document including instructions that load a browser plug-in configured to access a portion of a file system of the client device where the image files are located that the Internet browser application is restricted from accessing;

processing, by the Internet browser application, the markup language document to load the browser plug-in;

sending, by the Internet browser application, a request to the browser plug-in to access in the portion of the file system of the client device that the Internet browser application is restricted from accessing and upload one or more of the image files, the request including a first hash value that allows the browser plug-in to verify authenticity of a sender of the markup language document;

verifying, by the browser plug-in, the authenticity of the sender of the markup language document by:

determining a second hash value based on information in the received markup language document, and

comparing the first hash value to the second hash value, wherein a successful verification of the authenticity of the sender of the markup language document includes the first hash value matching the second hash value;

responsive to successful verification of the authenticity of the sender of the markup language document, accessing, by the browser plug-in, the portion of the file system identified in the request to upload the one or more of the image files;

receiving, by the Internet browser application, information describing progress of uploading the one or more of the image files; and

rendering, by the Internet browser application, a user interface element displaying the progress of uploading the one or more of the image files.

2. The computer implemented method of claim 1 , wherein uploading the one or more image files comprises retrieving information from the browser plug-in directly in a runtime environment of the Internet browser application.

3. The computer implemented method of claim 1 , wherein the browser plug-in is allowed direct access to the portion of the file system of the client device that the Internet browser application is restricted from accessing.

4. The computer implemented method of claim 1 , further comprising receiving a user selection of the one or more image files displayed on the client device.

5. The computer implemented method of claim 4 , further comprising:

receiving a request to start an upload process for uploading the one or more image files on the client device to a remote server; and

initiating the upload process to upload the one or more image files on the client device to a remote server.

6. The computer implemented method of claim 5 , further comprising:

receiving information describing the progress of the upload process; and

formatting for display, information describing the progress of the upload process by the client device.

7. A computer program product for allowing a browser application running on a client device to access image files stored on the client device, the computer program product comprising a non-transitory computer-readable storage medium containing a markup language document from a web application associated with an online system, the web application configured to upload image files from the client device to a web server of the online system, the markup language document comprising:

content items encoded in the markup language document, the markup language document including instructions that load a browser plug-in configured to access a portion of a file system of the client device where the image files are located that the browser application is restricted from accessing; and

instructions that, when interpreted by the browser application executing on the client device, cause the browser application to:

process the markup language document to load the browser plug-in;

send, by the browser application, a request to the browser plug-in to access the portion of the file system of the client device that the browser application is restricted from accessing and upload one or more of the image files, the request including a first hash value that allows the browser plug-in to verify authenticity of a sender of the markup language document;

verify, by the browser plug-in, the authenticity of the sender of the markup language document by:

determining a second hash value based on information in the received markup language document, and

comparing the first hash value to the second hash value, wherein a successful verification of the authenticity of the sender of the markup language document includes the first hash value matching the second hash value;

responsive to successful verification of the authenticity of the sender of the markup language document, access, by the browser plug-in, the resource in the portion of the file system identified in the request to upload the one or more of the image files;

receiving, by the browser application, information describing progress of uploading the one or more of the image files; and

rendering, by the Internet browser application, a user interface element displaying the progress uploading the one or more image files.

8. The computer program product of claim 7 , wherein the instruction that, when interpreted by the browser application executing on the client device further cause the browser application to:

receive a user selection of the one or more of the image files displayed on the client device.