Bump variations crash key limit.

This is apparently now being hit on Android Chromium builds as
a result of the field trial testing config.

Bug: 889950
Change-Id: Id1beefe02127726e1198c8a4fdb679a019a6e62b
Reviewed-on: https://chromium-review.googlesource.com/1249493Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594960}

components/variations/variations_crash_keys.cc

@@ -19,10 +19,10 @@ namespace variations {
 
 namespace {
 
-// Size of the "num-experiments" crash key in bytes. 2048 bytes should be able
-// to hold about 113 entries, given each entry is 18 bytes long (due to being
+// Size of the "num-experiments" crash key in bytes. 4096 bytes should be able
+// to hold about 227 entries, given each entry is 18 bytes long (due to being
 // of the form "8e7abfb0-c16397b7,").
-constexpr size_t kVariationsKeySize = 2048;
+constexpr size_t kVariationsKeySize = 4096;
 
 // Crash key reporting the number of experiments. 8 is the size of the crash key
 // in bytes, which is used to hold an int as a string.