Fix horizontal scroll tab-switching behavior on Linux

Fix horizontal scroll tab-switching behavior on Linux

The tab on the left side should be selected when scrolling to left and vice versa.

BUG=365501
TEST=Prepare a mouse with horizontal-scrolling feature, open multiple tabs, place cursor over tab strip and try to switch tabs.

Committed: https://crrev.com/ece9b5e4d3e45d874d893f8422be0796c26bb702
Cr-Commit-Position: refs/heads/master@{#325260}

[hashimoto, 2015-04-14 12:39:16]

hashimoto@chromium.org changed reviewers:
+ sky@chromium.org

[hashimoto, 2015-04-14 12:39:17]

sky@, could you review this change?

This shouldn't affect any platforms other than Linux as
browser_defaults::kScrollEventChangesTab is true only when defined(OS_LINUX) &&
!defined(OS_CHROMEOS).

[sky, 2015-04-14 19:52:34]

sky@chromium.org changed reviewers:
+ sadrul@chormium.org

[sky, 2015-04-14 19:52:35]

This LGTM, but Sadrul added this code. Sadrul, does the flip seem right to you?
Do you have a weird inverted horizontal mouse?

[hashimoto, 2015-04-15 10:03:41]

hashimoto@chromium.org changed reviewers:
+ sadrul@chromium.org

[hashimoto, 2015-04-15 10:03:41]

Sending to the right address.
sadrul@, how does this change look to you?

[sadrul, 2015-04-15 14:40:11]

Yeah, this lgtm.

[hashimoto, 2015-04-15 15:33:56]

The CQ bit was checked by hashimoto@chromium.org

[commit-bot: I haz the power, 2015-04-15 15:34:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1084903002/1

[commit-bot: I haz the power, 2015-04-15 16:31:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 16:32:16]

Patchset 1 (id:??) landed as
https://crrev.com/ece9b5e4d3e45d874d893f8422be0796c26bb702
Cr-Commit-Position: refs/heads/master@{#325260}