What precedent? I'm not aware of any precedent. (If you know of legal precedent, I would like to know about it. IANAL, but I intend to play one someday.)
Also, it's worth noting that Edward Naughton's description of Sega Enterprises v. Accolade (9th Cir. 1992) is totally wrong. (Atrociously wrong, in fact.) He used it as a possible defense for Google, but that case is quite the opposite. First of all, his description is totally wrong. Sega v. Accolade said that the disassembly *was* copyright infringement, but that it was a Fair Use. And it said that it was a Fair Use *not* because the copied code embodied the *idea* of interoperability (it rejected that subject-matter argument, as have most other courts), but only because it was the only way to get at otherwise uncopyrightable material.
In other words, the idea that particular source code is not copyrightable because it "merges" with the idea of interoperability or compatibility with an operating system is a bogus argument. (Rejected in Sega; rejected in Apple Computer v. Franklin Computer (3d Cir. 1983). Rejected in other cases.) The only way Google's theory holds water is if the source code at question itself is completely uncopyrightable, whether in a header file or any other file. And that means it must be bereft of any original creativity. (Under the Feist analysis, which found no copyright in a phone book because it listed residences in alphabetical order--an uncreative compilation of facts; begging the question of whether some other creative listing not in alphabetical order might be sufficient creativity to protect the phone book.)
Frankly, as a programmer I'm not so sure I want Google to be right.
Google can be wrong yet Android applications still be safe. Google could be wrong that a 10-line inline function is not copyrightable; but correct that a typedef is not copyrightable. And as long as the app only depends on the typedef and not the inline function, all is fine. Google will merely have to stop stripping copyright notices from source files--GPLv2 sec. 1 requires that the licensee "keep intact all the notices that refer to this License."
I suspect Google's legal theory is born of the abstraction/filtration/comparison test described in Computer Associates v. Altai, 982 F.2d 693 (2d Cir. 1992). Reading the case, or part III, or at least section III.A(2), is like a mini-education in copyright law as applied to computer programs. http://www.bitlaw.com/source/cases/copyright/altai.html