[Impeller] libImpeller: Respect the paragraph style line height specification.

impeller/toolkit/interop/impeller.h

@@ -2143,7 +2143,12 @@ void ImpellerParagraphStyleSetFontSize(
     float size);
 
 //------------------------------------------------------------------------------
-/// @brief      Set the paragraph height.
+/// @brief      The height of the text as a multiple of text size.
+///
+///             When height is 0.0, the line height will be determined by the
+///             font's metrics directly, which may differ from the font size.
+///             Otherwise the line height of the text will be a multiple of font
+///             size, and be exactly fontSize * height logical pixels tall.
 ///
 /// @param[in]  paragraph_style  The paragraph style.
 /// @param[in]  height           The height.

impeller/toolkit/interop/impeller_unittests.cc

@@ -207,6 +207,7 @@ TEST_P(InteropPlaygroundTest, CanCreateParagraphs) {
   auto style = Adopt<ParagraphStyle>(ImpellerParagraphStyleNew());
   ASSERT_TRUE(style);
   ImpellerParagraphStyleSetFontSize(style.GetC(), 150.0f);
+  ImpellerParagraphStyleSetHeight(style.GetC(), 2.0f);
 
   {
     auto paint = Adopt<Paint>(ImpellerPaintNew());

impeller/toolkit/interop/paragraph_style.cc

@@ -28,6 +28,7 @@ void ParagraphStyle::SetFontSize(double size) {
 
 void ParagraphStyle::SetHeight(double height) {
   style_.height = height;
+  style_.has_height_override = (height != 0.0);
 }
 
 void ParagraphStyle::SetTextAlignment(txt::TextAlign alignment) {