[WebProfilerBundle] Fixed IE8 support
bug #12900 [WebProfilerBundle] Fixed IE8 support (korotovsky)

This PR was merged into the 2.6 branch.

Discussion
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[WebProfilerBundle] Fixed IE8 support

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

Commits
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a6dd6c9 [WebProfilerBundle] Fixed IE8 support