11. One or more non-transitory computer storage devices having instructions stored thereon that, when executed by a computer, cause the computer to perform operations comprising: receiving, by a search application installed on a user device, a query entered by a user of the user device; providing, by the search application, the query to a plurality of third-party applications installed on the user device, other than the search application; receiving, by the search application, a respective set of search results from each of the third-party applications as a respective response to the query, wherein each respective set of search results identifies data managed by the respective third-party application from which the respective set of search results is received, wherein at least one of the respective sets of search results includes multiple search results; integrating, by the search application, the respective sets of search results from the third-party applications into an integrated result set that includes groups of search results, wherein each group of search results corresponds to a different third-party application among the plurality of third-party applications and includes only the respective set of search results received from the corresponding third-party application; identifying, for each respective third-party application among the plurality of third-party applications, a respective score that indicates a number of user selections of search results from the respective third-party application that have previously occurred on the user device; ranking the groups of search results in the integrated result set based on the respective scores for the third-party applications that correspond to the groups of search results; and presenting, by the search application, the integrated result set on the user device in an arrangement that corresponds to the ranking of the groups of search results in the integrated result set.
11. One or more non-transitory computer storage devices having instructions stored thereon that, when executed by a computer, cause the computer to perform operations comprising: receiving, by a search application installed on a user device, a query entered by a user of the user device; providing, by the search application, the query to a plurality of third-party applications installed on the user device, other than the search application; receiving, by the search application, a respective set of search results from each of the third-party applications as a respective response to the query, wherein each respective set of search results identifies data managed by the respective third-party application from which the respective set of search results is received, wherein at least one of the respective sets of search results includes multiple search results; integrating, by the search application, the respective sets of search results from the third-party applications into an integrated result set that includes groups of search results, wherein each group of search results corresponds to a different third-party application among the plurality of third-party applications and includes only the respective set of search results received from the corresponding third-party application; identifying, for each respective third-party application among the plurality of third-party applications, a respective score that indicates a number of user selections of search results from the respective third-party application that have previously occurred on the user device; ranking the groups of search results in the integrated result set based on the respective scores for the third-party applications that correspond to the groups of search results; and presenting, by the search application, the integrated result set on the user device in an arrangement that corresponds to the ranking of the groups of search results in the integrated result set. 19. The one or more non-transitory computer storage devices of claim 11 , wherein the operations further comprise: receiving a user selection in the search application of a search result from a particular application among the plurality of third-party applications; and modifying, in response to receiving the user selection of the search result from the particular application, the respective score for the particular application so as to increase a likelihood that a group of search results corresponding to the particular application will be ranked higher by the search application in an integrated result set for a subsequent search session.