Indexing application pages of native applications

1. A computer-implemented method performed by data processing apparatus comprising one or more computers in data communication, the method comprising:

instantiating a virtual machine emulating an operating system of a user device;

instantiating, within the virtual machine, a native application that generates application pages for display on a user device within the native application, the native application operating independent of a browser application that can operate on the user device;

accessing, within the virtual machine, application pages of the native application, and for each of the application pages:

extracting content from the application page, the content including content of a plurality of different content types, the content for each content type being extracted by a corresponding extractor specific to that content type;

generating application page data describing content of the application page, the content described by the application page data including text that a user device displays on the application page when the user device displays the application page; and

indexing the application page data for the native application in an index that is searchable by a search engine.

2. The computer implemented method of claim 1 , wherein the indexing comprises indexing the application page for the native application by a combination of a uniform resource identifier (URI) of the application page and a unique application identifier that identifiers the native application.

3. The computer-implemented method of claim 1 , further comprising:

receiving, from a publisher of the native application, data specifying application pages to be indexed for the native application; and

accessing application pages of the native application comprises accessing only the application pages that are specified to be indexed for the native application.

4. The computer-implemented method of claim 1 , wherein the extractor types include a text extractor specific to a text content type and an image extractor specific to an image content type.

5. The computer-implemented method of claim 4 , wherein the content described by the application page data further includes image data depicting an image of the application page.

6. The computer-implemented method of claim 5 , wherein generating application page data describing content of the application page comprises:

performing optical character recognition (OCR) on the image data to generate OCR text; and

generating, based on the OCR text, text data describing the text that a user device displays on the application page.

7. The computer-implemented method of claim 1 , wherein the content described by the application page data further includes application page link data describing at least one link within the application page that links to another application page.

8. The computer-implemented method of claim 1 , wherein the content described by the application page data further includes web page link data describing at least one link within the application page that links to a resource referenced by a uniform resource locator that, when selected, instantiates a browser application that renders the resource in a browser environment separate from the native application.

9. A system, comprising:

a data processing apparatus; and

software stored in non-transitory computer readable storage medium storing instructions executable by the data processing apparatus and that upon such execution cause the data processing apparatus to perform operations comprising:

instantiating a virtual machine emulating an operating system of a user device;

instantiating, within the virtual machine, a native application that generates application pages for display on a user device within the native application, the native application operating independent of a browser application that can operate on the user device;

accessing, within the virtual machine, application pages of the native application, and for each of the application pages:

extracting content from the application page, the content including content of a plurality of different content types, the content for each content type being extracted by a corresponding extractor specific to that content type;

generating application page data describing content of the application page, the content described by the application page data including text that a user device displays on the application page when the user device displays the application page; and

indexing the application page data for the native application in an index that is searchable by a search engine.

10. The system of claim 9 , wherein the indexing comprises indexing the application page for the native application by a combination of a uniform resource identifier (URI) of the application page and a unique application identifier that identifiers the native application.

11. The system of claim 9 , the operations further comprising:

receiving, from a publisher of the native application, data specifying application pages to be indexed for the native application; and

accessing application pages of the native application comprises accessing only the application pages that are specified to be indexed for the native application.

12. The system of claim 9 , wherein the extractor types include a text extractor specific to a text content type and an image extractor specific to an image content type.

13. The system of claim 11 , wherein the content described by the application page data further includes image data depicting an image of the application page.

14. The system of claim 13 , wherein generating application page data describing content of the application page comprises:

performing optical character recognition (OCR) on the image data to generate OCR text; and

generating, based on the OCR text, text data describing the text that a user device displays on the application page.

15. The system of claim 9 , wherein the content described by the application page data further includes application page link data describing at least one link within the application page that links to another application page.

16. The system of claim 9 , wherein the content described by the application page data further includes web page link data describing at least one link within the application page that links to a resource referenced by a uniform resource locator that, when selected, instantiates a browser application that renders the resource in a browser environment separate from the native application.

17. A non-transitory computer readable storage medium storing instructions executable by a data processing apparatus and that upon such execution cause the data processing apparatus to perform operations comprising:

instantiating a virtual machine emulating an operating system of a user device;

instantiating, within the virtual machine, a native application that generates application pages for display on a user device within the native application, the native application operating independent of a browser application that can operate on the user device;

accessing, within the virtual machine, application pages of the native application, and for each of the application pages:

extracting content from the application page, the content including content of a plurality of different content types, the content for each content type being extracted by a corresponding extractor specific to that content type;

generating application page data describing content of the application page, the content described by the application page data including text that a user device displays on the application page when the user device displays the application page; and

indexing the application page data for the native application in an index that is searchable by a search engine.