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. 17. The one or more non-transitory computer storage devices of claim 11 , wherein: the user device includes one or more operating system components; the operations comprise: providing, by the search application, the query to the one or more operating system components and to one or more remote search services remote from the user device; and integrating, by the search application, respective sets of search results received from the one or more operating system components and the one or more remote search services with the sets of search results from the third-party applications to form the integrated result set.