Enable all DistillerPageWebContentsTest tests

Enabled:
- DistillerPageWebContentsTest.UsingCurrentWebContentsReadyForDistillation
- DistillerPageWebContentsTest.UsingCurrentWebContentsNotFinishedLoadingYet

These tests were reported flaky, but couldn't repro locally. Re-enable
to get more info on bots.

BUG=648578

Change-Id: Ifee5adf4fded7d549d8480d5148c603c45319fe3
Reviewed-on: https://chromium-review.googlesource.com/566591Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487178}

components/dom_distiller/content/browser/distiller_page_web_contents_browsertest.cc

@@ -313,7 +313,7 @@ IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest,
 }
 
 IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest,
-                       DISABLED_UsingCurrentWebContentsNotFinishedLoadingYet) {
+                       UsingCurrentWebContentsNotFinishedLoadingYet) {
   std::string url(kSimpleArticlePath);
   bool expect_new_web_contents = false;
   bool setup_main_frame_observer = true;
@@ -325,7 +325,7 @@ IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest,
 }
 
 IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest,
-                       DISABLED_UsingCurrentWebContentsReadyForDistillation) {
+                       UsingCurrentWebContentsReadyForDistillation) {
   std::string url(kSimpleArticlePath);
   bool expect_new_web_contents = false;
   bool setup_main_frame_observer = true;