Fix some nits in dash drawing code.

Just write "0.1f" instead of "1.0f / 10". Also fix various nits in
surrounding code.

Change-Id: Ie51ee8527fd2484c0097a80e6c727864f16e45c4
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/70736
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

core/fxge/agg/fx_agg_driver.cpp

diff --git a/core/fxge/agg/fx_agg_driver.cpp b/core/fxge/agg/fx_agg_driver.cpp
index c92c6be..09474b4 100644
--- a/core/fxge/agg/fx_agg_driver.cpp
+++ b/core/fxge/agg/fx_agg_driver.cpp
@@ -292,7 +292,7 @@
     for (size_t i = 0; i < (pGraphState->m_DashArray.size() + 1) / 2; i++) {
       float on = pGraphState->m_DashArray[i * 2];
       if (on <= 0.000001f)
-        on = 1.0f / 10;
+        on = 0.1f;
       float off = i * 2 + 1 == pGraphState->m_DashArray.size()
                       ? on
                       : pGraphState->m_DashArray[i * 2 + 1];

core/fxge/skia/fx_skia_device.cpp

diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index 9187f53..6f9f471 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -1588,12 +1588,11 @@
     for (size_t i = 0; i < count; i++) {
       float on = pGraphState->m_DashArray[i * 2];
       if (on <= 0.000001f)
-        on = 1.f / 10;
+        on = 0.1f;
       float off = i * 2 + 1 == pGraphState->m_DashArray.size()
                       ? on
                       : pGraphState->m_DashArray[i * 2 + 1];
-      if (off < 0)
-        off = 0;
+      off = std::max(off, 0.0f);
       intervals.get()[i * 2] = on;
       intervals.get()[i * 2 + 1] = off;
     }

core/fxge/win32/fx_win32_gdipext.cpp

diff --git a/core/fxge/win32/fx_win32_gdipext.cpp b/core/fxge/win32/fx_win32_gdipext.cpp
index 20cf77f..958c64c 100644
--- a/core/fxge/win32/fx_win32_gdipext.cpp
+++ b/core/fxge/win32/fx_win32_gdipext.cpp
@@ -446,15 +446,15 @@
       on_phase /= width;
       off_phase /= width;
       if (on_phase + off_phase <= 0.00002f) {
-        on_phase = 1.0f / 10;
-        off_phase = 1.0f / 10;
+        on_phase = 0.1f;
+        off_phase = 0.1f;
       }
       if (bDashExtend) {
         if (off_phase < 1)
           off_phase = 0;
         else
-          off_phase -= 1;
-        on_phase += 1;
+          --off_phase;
+        ++on_phase;
       }
       if (on_phase == 0 || off_phase == 0) {
         if (nCount == 0) {