base/stl_util.h has ContainsKey() and ContainsValue() [1]
helper functions to find a Key or a Value in a Container,
respectively. With ScopedVector being deprecated, snippets
of the form

std::vector<std::unique_ptr<Typename>> haystack;

std::find_if(haystack.begin(),
             haystack.end(),
             [needle](const std::unique_ptr<Typename>& entry) {
               return entry.get() == needle;
             });

can be found in the code. 

Consider extending/specialising ContainsValue() or adding 
a ContainsPointedValue() and using it throughout.

[1] https://cs.chromium.org/chromium/src/base/stl_util.h?sq=package:chromium&dr=CSs&l=196