[sql] Test helpers to ease testing of simple queries.

ExecuteWithResult() returns the first column of the first row as a
string, ExecuteWithResults() formats the results with column and row
separators.  They make it easier to check results using EXPECT_EQ().

BUG=none

Review-Url: https://codereview.chromium.org/2441153002
Cr-Commit-Position: refs/heads/master@{#427520}
3 files changed