Increase hint text contrast ratio to 4.5 (#15504)

packages/flutter/lib/src/material/input_decorator.dart

@@ -2305,31 +2305,18 @@ class InputDecorationTheme extends Diagnosticable {
   void debugFillProperties(DiagnosticPropertiesBuilder description) {
     super.debugFillProperties(description);
     const InputDecorationTheme defaultTheme = const InputDecorationTheme();
-    description.add(new DiagnosticsProperty<TextStyle>('labelStyle', labelStyle,
-        defaultValue: defaultTheme.labelStyle));
-    description.add(new DiagnosticsProperty<TextStyle>('helperStyle', helperStyle,
-        defaultValue: defaultTheme.helperStyle));
-    description.add(new DiagnosticsProperty<TextStyle>('hintStyle', hintStyle,
-        defaultValue: defaultTheme.hintStyle));
-    description.add(new DiagnosticsProperty<TextStyle>('errorStyle', errorStyle,
-        defaultValue: defaultTheme.errorStyle));
-    description
-        .add(new DiagnosticsProperty<bool>('isDense', isDense, defaultValue: defaultTheme.isDense));
-    description.add(new DiagnosticsProperty<EdgeInsets>('contentPadding', contentPadding,
-        defaultValue: defaultTheme.contentPadding));
-    description.add(new DiagnosticsProperty<bool>('isCollapsed', isCollapsed,
-        defaultValue: defaultTheme.isCollapsed));
-    description.add(new DiagnosticsProperty<TextStyle>('prefixStyle', prefixStyle,
-        defaultValue: defaultTheme.prefixStyle));
-    description.add(new DiagnosticsProperty<TextStyle>('suffixStyle', suffixStyle,
-        defaultValue: defaultTheme.suffixStyle));
-    description.add(new DiagnosticsProperty<TextStyle>('counterStyle', counterStyle,
-        defaultValue: defaultTheme.counterStyle));
-    description
-        .add(new DiagnosticsProperty<bool>('filled', filled, defaultValue: defaultTheme.filled));
-    description.add(new DiagnosticsProperty<Color>('fillColor', fillColor,
-        defaultValue: defaultTheme.fillColor));
-    description.add(
-        new DiagnosticsProperty<InputBorder>('border', border, defaultValue: defaultTheme.border));
+    description.add(new DiagnosticsProperty<TextStyle>('labelStyle', labelStyle, defaultValue: defaultTheme.labelStyle));
+    description.add(new DiagnosticsProperty<TextStyle>('helperStyle', helperStyle, defaultValue: defaultTheme.helperStyle));
+    description.add(new DiagnosticsProperty<TextStyle>('hintStyle', hintStyle, defaultValue: defaultTheme.hintStyle));
+    description.add(new DiagnosticsProperty<TextStyle>('errorStyle', errorStyle, defaultValue: defaultTheme.errorStyle));
+    description.add(new DiagnosticsProperty<bool>('isDense', isDense, defaultValue: defaultTheme.isDense));
+    description.add(new DiagnosticsProperty<EdgeInsets>('contentPadding', contentPadding, defaultValue: defaultTheme.contentPadding));
+    description.add(new DiagnosticsProperty<bool>('isCollapsed', isCollapsed, defaultValue: defaultTheme.isCollapsed));
+    description.add(new DiagnosticsProperty<TextStyle>('prefixStyle', prefixStyle, defaultValue: defaultTheme.prefixStyle));
+    description.add(new DiagnosticsProperty<TextStyle>('suffixStyle', suffixStyle, defaultValue: defaultTheme.suffixStyle));
+    description.add(new DiagnosticsProperty<TextStyle>('counterStyle', counterStyle, defaultValue: defaultTheme.counterStyle));
+    description.add(new DiagnosticsProperty<bool>('filled', filled, defaultValue: defaultTheme.filled));
+    description.add(new DiagnosticsProperty<Color>('fillColor', fillColor, defaultValue: defaultTheme.fillColor));
+    description.add(new DiagnosticsProperty<InputBorder>('border', border, defaultValue: defaultTheme.border));
   }
 }

packages/flutter/lib/src/material/theme_data.dart

@@ -146,7 +146,7 @@ class ThemeData extends Diagnosticable {
     backgroundColor ??= isDark ? Colors.grey[700] : primarySwatch[200];
     dialogBackgroundColor ??= isDark ? Colors.grey[800] : Colors.white;
     indicatorColor ??= accentColor == primaryColor ? Colors.white : accentColor;
-    hintColor ??= isDark ? const Color(0x42FFFFFF) : const Color(0x4C000000);
+    hintColor ??= isDark ?  const Color(0x80FFFFFF) : const Color(0x8A000000);
     errorColor ??= Colors.red[700];
     inputDecorationTheme ??= const InputDecorationTheme();
     iconTheme ??= isDark ? const IconThemeData(color: Colors.white) : const IconThemeData(color: Colors.black);