make not to initialize webview repeatedly (failure)
Revert "make not to initialize webview repeatedly (failure)"

This reverts commit 06c4461b84681c4b8f89961a92789a8bcce8cd22.
observe onCreateView of DummySectionFragment
setRetainInstance(true);

ref.
  http://developer.android.com/reference/android/app/Fragment.html#setRetainInstance%28boolean%29
  http://www18.atwiki.jp/bovecrach/pages/14.html
setRetainInstance(false);
Revert "setRetainInstance(false);"

This reverts commit 76093f5e5cf1508573ed2fef06e6ec84503c5ae6.
Revert "setRetainInstance(true);"

This reverts commit 2bc4094461334bd1ca408624215bb50280ebdd3e.
Merge branch 'research-fragment'