I read a report yesterday that suggested that Google was responsible for at least 23% of Apple's services revenue. How you may ask, Google and Apple are huge rivals in the mobile space?
As Apple mentioned in their results, they now have 900 million active iPhones and 1.4bn active devices. That has a lot of value. Google pay Apple billions of Dollars every year to make Google search the default on these devices. You see, Google already steers android users to their search. But Apple clients could be swayed to other engines (not that they would want to). This is how Google can lock in an extra billion clients.
As eyes have shifted away from desktops and on to mobile screens, it has been crucial for internet businesses to adapt. Google's free Android service sounds like a charity but in truth it keeps the mobile eyes on their product and that is all they care about.
Don't feel too bad for Google and their relationship with Apple. Apple outsource a lot of their cloud services to Google, so the money flows both ways.