Enable DPI awareness in unittest

The browser process is DPI aware.

To be able to detect correctly the configuration on my win10 computer,
I needed to add the code of this CL.

To make the tests fails, I needed to change the system config to
increase it to 125%, then I needed to sign-out and sign-in.

see the output:

../../chrome/browser/ui/views/layout_provider_unittest.cc(70): error: Expected equality of these values:
  system_dpi_scale
    Which is: 1.25
  1.0
    Which is: 1
The test requires default display settings. The DPI of the display is not 100%. dpi_scale=1.25
Stack trace:
Backtrace:
        base::debug::StackTrace::StackTrace [0x00007FFB86ADC648+40] (C:\src\chromium\src\base\debug\stack_trace.cc:203)
        StackTraceGetter::CurrentStackTrace [0x00007FF66C1DB986+86] (C:\src\chromium\src\third_party\googletest\custom\gtest\internal\custom\stack_trace_getter.cc:24)
        testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop [0x00007FF66C1F172A+90] (C:\src\chromium\src\third_party\googletest\src\googletest\src\gtest.cc:827)
        testing::internal::AssertHelper::operator= [0x00007FF66C1F11F7+87] (C:\src\chromium\src\third_party\googletest\src\googletest\src\gtest.cc:404)
        LayoutProviderTest::SetUpTestSuite [0x00007FF66B9EA76D+1117] (C:\src\chromium\src\chrome\browser\ui\views\layout_provider_unittest.cc:70)
R=tapted@chromium.org
Bug: 963868

Change-Id: Ifcda84cbea88c42e9d3b2c5c81c024a1a9abc371
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1630978
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665182}

chrome/browser/ui/views/layout_provider_unittest.cc

@@ -25,6 +25,7 @@
 #endif
 
 #if defined(OS_WIN)
+#include "base/win/win_util.h"
 #include "base/win/windows_version.h"
 #include "ui/display/win/dpi.h"
 #include "ui/gfx/system_fonts_win.h"
@@ -49,6 +50,7 @@ class LayoutProviderTest : public testing::Test {
  protected:
   static void SetUpTestSuite() {
 #if defined(OS_WIN)
+    base::win::EnableHighDPISupport();
     gfx::win::InitializeDirectWrite();
 
     // Ensures anti-aliasing is activated.