Use longer timeout for tests in CopylessPasteTest

Increasing timeout (https://codereview.chromium.org/2826253004)
lowered the failure rate. This indicates the tests are not inherently
flaky. They just run for longer.

Bug: 713172, 747073
Change-Id: I20a039776aa2aa9f70560e8d688f27ef34e6eb6a
Reviewed-on: https://chromium-review.googlesource.com/580256Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488448}

chrome/android/javatests/src/org/chromium/chrome/browser/CopylessPasteTest.java

@@ -49,7 +49,7 @@ public class CopylessPasteTest {
     public ChromeTabbedActivityTestRule mActivityTestRule = new ChromeTabbedActivityTestRule();
 
     // The default timeout (in seconds) for a callback to wait.
-    public static final long WAIT_TIMEOUT_SECONDS = scaleTimeout(10);
+    public static final long WAIT_TIMEOUT_SECONDS = scaleTimeout(20);
 
     // NODATA_PAGE doesn't contain desired metadata.
     private static final String NODATA_PAGE = "/chrome/test/data/android/about.html";