Allow strings containing '.' after sign (ex: -.8) in Decimal::FromString.

Entering those strings in a <input type=number> leads to validation messages not being displayed in certain cases:
- rangeUnderflow (bug985330)
- rangeOverflow
- stepMisMatch

This is due to Decimal::FromString not recognizing it as valid, hence returning NaN incorrectly. decimal.h and the spec:
https://html.spec.whatwg.org/#valid-floating-point-number say it should be supported.

Fixes it and adds appropriate tests in wtf_unittests and in web_tests.

Bug: 985330
Change-Id: Ic3a3bb1ca855ebcc13f96aac16c31937a2cba0cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773262
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693074}

third_party/blink/renderer/platform/wtf/decimal.cc

@@ -787,6 +787,7 @@ Decimal Decimal::FromString(const String& str) {
         }
 
         HandleCharAndBreak('0', kStateZero);
+        HandleCharAndBreak('.', kStateDot);
         return Nan();
 
       case kStateStart:

third_party/blink/renderer/platform/wtf/decimal_test.cc

@@ -668,6 +668,8 @@ TEST_F(DecimalTest, FromString) {
   EXPECT_EQ(Encode(3, 0, kPositive), FromString("+3"));
   EXPECT_EQ(Encode(0, 3, kPositive), FromString("0E3"));
   EXPECT_EQ(Encode(5, -1, kPositive), FromString(".5"));
+  EXPECT_EQ(Encode(5, -1, kPositive), FromString("+.5"));
+  EXPECT_EQ(Encode(5, -1, kNegative), FromString("-.5"));
   EXPECT_EQ(Encode(100, 0, kPositive), FromString("100"));
   EXPECT_EQ(Encode(100, 0, kNegative), FromString("-100"));
   EXPECT_EQ(Encode(123, -2, kPositive), FromString("1.23"));

third_party/blink/web_tests/external/wpt/html/semantics/forms/constraints/form-validation-validity-rangeOverflow.html

@@ -106,7 +106,8 @@
         {conditions: {max: "5", value: "1abc"}, expected: false, name: "[target] The value is not a number"},
         {conditions: {max: "5", value: "6"}, expected: true, name: "[target] The value is greater than max(integer)"},
         {conditions: {max: "-5.5", value: "-5.4"}, expected: true, name: "[target] The value is greater than max(floating number)"},
-        {conditions: {max: "-5e-1", value: "5e+2"}, expected: true, name: "[target] The value is greater than max(scientific notation)"}
+        {conditions: {max: "-1", value: "-.8"}, expected: true, name: "[target] The value is greater than max(special floating number)"},
+        {conditions: {max: "-5e-1", value: "5e+2"}, expected: true, name: "[target] The value is greater than max(scientific notation)"},
       ]
     }
    ];

third_party/blink/web_tests/external/wpt/html/semantics/forms/constraints/form-validation-validity-rangeUnderflow.html

@@ -104,6 +104,7 @@
         {conditions: {min: "5", value: "6abc"}, expected: false, name: "[target] The value is not a number"},
         {conditions: {min: "6", value: "5"}, expected: true, name: "[target] The value is less than min(integer)"},
         {conditions: {min: "-5.4", value: "-5.5"}, expected: true, name: "[target] The value is less than min(floating number)"},
+        {conditions: {min: "1", value: "-.8"}, expected: true, name: "[target] The value is less than min(special floating number)"},
         {conditions: {min: "5e+2", value: "-5e-1"}, expected: true, name: "[target] The value is less than min(scientific notation)"}
       ]
     }

third_party/blink/web_tests/external/wpt/html/semantics/forms/constraints/form-validation-validity-stepMismatch.html

@@ -66,7 +66,8 @@
       types: ["number"],
       testData: [
         {conditions: {step: "", value: "1"}, expected: false, name: "[target] The step attribute is not set"},
-        {conditions: {step: 2 * 1 * 1, value: ""}, expected: false, name: "[target] The value attibute is empty string"},
+        {conditions: {step: "", value: "-.8"}, expected: true, name: "[target] The step attribute is not set and the value attribute is a floating number"},
+        {conditions: {step: 2 * 1 * 1, value: ""}, expected: false, name: "[target] The value attribute is empty string"},
         {conditions: {step: 2 * 1 * 1, value: "2"}, expected: false, name: "[target] The value must match the step"},
         {conditions: {step: 2 * 1 * 1, value: "3"}, expected: true, name: "[target] The value must mismatch the step"}
       ]

third_party/blink/web_tests/fast/forms/number/number-validity-rangeoverflow-expected.txt

@@ -15,6 +15,7 @@ PASS The value "0.999999999999999999999999999999999999999999" doesn't overflow t
 PASS The value "101" overflows the maximum value "100".
 PASS The value "-99" overflows the maximum value "-100".
 PASS The value "101" overflows the maximum value "1E+2".
+PASS The value "-.8" overflows the maximum value "-1".
 PASS The value "101" overflows the maximum value "100".
 PASS The value "101" doesn't overflow the maximum value "1E+2" when disabled.
 PASS successfullyParsed is true

third_party/blink/web_tests/fast/forms/number/number-validity-rangeoverflow.html

@@ -57,6 +57,8 @@ checkNotOverflow('0.999999999999999999999999999999999999999999', '0.999999999999
 checkOverflow('101', '100');
 checkOverflow('-99', '-100');
 checkOverflow('101', '1E+2');
+input.min = '-2';
+checkOverflow('-.8', '-1');
 input.min = '200';  // value < min && value > max
 checkOverflow('101', '100');
 

third_party/blink/web_tests/fast/forms/number/number-validity-rangeunderflow-expected.txt

@@ -16,6 +16,7 @@ PASS The value "99" undeflows the minimum value "100".
 PASS The value "-101" undeflows the minimum value "-100".
 PASS The value "99" undeflows the minimum value "1E+2".
 PASS The value "101" undeflows the minimum value "200".
+PASS The value "-.8" undeflows the minimum value "1".
 PASS The value "99" doesn't underflow the minimum value "1E+2" when disabled.
 PASS successfullyParsed is true
 

third_party/blink/web_tests/fast/forms/number/number-validity-rangeunderflow.html

@@ -61,6 +61,7 @@ checkUnderflow('-101', '-100');
 checkUnderflow('99', '1E+2');
 input.max = '100';  // value < min && value > max
 checkUnderflow('101', '200');
+checkUnderflow('-.8', '1');
 
 // Disabled
 checkNotUnderflow('99', '1E+2', true);

third_party/blink/web_tests/fast/forms/number/number-validity-stepmismatch-expected.txt

@@ -27,6 +27,7 @@ PASS stepMismatchFor("0.9", "0.1", "") is false
 PASS stepMismatchFor("0.9", "0.1000001", "") is true
 PASS stepMismatchFor("0.9", "0.1000000000000001", "") is false
 PASS stepMismatchFor("1.0", "0.3333333333333333", "") is false
+PASS stepMismatchFor("-.8", null, "-1") is true
 Rounding
 PASS stepMismatchFor("5.005", "0.005", "4") is false
 Disabled

third_party/blink/web_tests/fast/forms/number/number-validity-stepmismatch.html

@@ -45,6 +45,7 @@ shouldBe('stepMismatchFor("0.9", "0.1", "")', 'false');
 shouldBe('stepMismatchFor("0.9", "0.1000001", "")', 'true');
 shouldBe('stepMismatchFor("0.9", "0.1000000000000001", "")', 'false');
 shouldBe('stepMismatchFor("1.0", "0.3333333333333333", "")', 'false');
+shouldBe('stepMismatchFor("-.8", null, "-1")', 'true');
 debug('Rounding');
 shouldBe('stepMismatchFor("5.005", "0.005", "4")', 'false');
 debug('Disabled');